Compact high power alternator

ABSTRACT

An apparatus for converting between mechanical and electrical energy, particularly suited for use as a compact high power alternator for automotive use and “remove and replace” retrofitting of existing vehicles. Various aspects of the invention provide a means of significantly increasing the output of permanent magnet alternators while addressing the issues of radial loading applied to a permanent magnet alternator rotor. Another aspect of the invention allows for the production of power in two discrete voltages. An aspect of this invention allows for a marked increase in output capability without increasing axial length through the use of magnetic fringing. One aspect of the invention offers an effective means of mounting a skewed stack that eliminates or reduces cogging that is present in a permanent magnet machine without negatively impacting airflow. Another aspect of the invention reduces cogging by radially offsetting opposing magnets of a dual rotor permanent magnet machine.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of and claims priority to U.S. patentapplication Ser. No. 12/368,212, filed Feb. 9, 2009 which claimspriority to U.S. Provisional Application No. 61/026,954, filed Feb. 7,2008, the contents of which are incorporated herein in their entirety.

DESCRIPTION OF THE INVENTION

1. Field of the Invention

The present invention relates to machines for converting betweenmechanical and electrical energy, and in particular to compact highpower alternators using permanent magnets.

2. Background of the Invention

An alternator typically comprises a rotor mounted on a rotating shaftand disposed concentrically and interior relative to a stationarystator. Alternatively, a stator may be positioned concentrically withina rotor. An external energy source, such as a motor or turbine, commonlydrives the rotating element, directly or through an intermediate systemsuch as a pulley belt. Both the stator and the rotor have a series ofpoles. Either the rotor or the stator generates a magnetic field, whichinteracts with windings on the poles of the other structure. As themagnetic field intercepts the windings, an electrical current isgenerated, which is provided to a suitable load. The induced current istypically applied to a bridge rectifier, sometimes regulated, andprovided as an output. In some instances, the regulated output signal isapplied to an inverter to provide an AC output.

Conversely, the device can act as a motor if an appropriate electricalsignal is applied to the windings.

In general, permanent magnet alternators are well-known. Suchalternators use permanent magnets to generate the requisite magneticfield. Permanent magnet generators tend to be much lighter and smallerthan traditional wound field generators. Examples of permanent magnetalternators are described in U.S. Pat. No. 5,625,276 issued to Scott etal. on Apr. 29, 1997; U.S. Pat. No. 5,705,917 issued to Scott et al. onJan. 6, 1998; U.S. Pat. No. 5,886,504 issued to Scott et al. on Mar. 23,1999; U.S. Pat. No. 5,929,611 issued to Scott et al. on Jul. 27 1999;U.S. Pat. No. 6,034,511 issued to Scott et al. on Mar. 7, 2000; and U.S.Pat. No. 6,441,222 issued to Scott on Aug. 27, 2002, and U.S.application Ser. No. 10/889,980 entitled “Compact High Power Alternator”filed on Jul. 12, 2004 by Lafontaine, et al. (hereinafter referred to asthe “Lafontaine et al. application”). To the extent not inconsistentwith disclosures of embodiments of the present invention herein, theabovementioned references are fully incorporated by reference herein forall purposes.

The power supplied by a permanent magnet generator varies significantlyaccording to the speed of the rotor. In many applications, changes inthe rotor speed are common due to, for example, engine speed variationsin an automobile, or changes in load characteristics. Accordingly, anelectronic control system is typically employed. An example of apermanent magnet alternator and control systems therefore is describedin the aforementioned U.S. Pat. No. 5,625,276 issued to Scott et al. onApr. 29, 1997. Examples of other control systems are described in U.S.Pat. No. 6,018,200 issued to Anderson, et al. on Jan. 25, 2000. To theextent not inconsistent with disclosures of embodiments of the presentinvention herein, the abovementioned references are fully incorporatedby reference herein for all purposes.

In such permanent magnet alternators, the efficiency is inverselyproportional to the “air gap” separating the magnets from the stator.Such air gaps are often in the range of 20 to 40 thousands of an inch.The output produced by a stator is proportional to the square of the airgap diameter (additionally defined in relation to FIG. 1F, below),therefore it is particularly advantageous to maximize the air gapdiameter as is allowed by the particular application.

Typically alternators in automotive applications are equipped withmounting appendages, more commonly known as mounting lugs that are usedto both fasten the alternator to the engine block by means of anintermediate bracket and to allow the alternator to function properlywithout belt slippage by a means that will be described later. A commonarrangement known as a J180 or hinge type mount, (also known as athree-point mount) includes three mounting lugs for that purpose. Two ofthe mounting lugs are located at the front and rear of the alternatorand are in alignment axially. The two aligned lugs are fasten to acorresponding structure on the engine by use of a bolt passing throughthe two lugs and mounting bracket to in effect act as a hinge. A thirdmounting lug, commonly known as the upper adjusting lug, is typicallypositioned on the front portion of the alternator and is in oppositionradially from the first two lugs. The upper adjusting lug is mounted toa device equipped with a jackscrew to both rotate the alternator aboutthe hinge formed by the first two lugs and to lock the alternator inplace once proper belt tension is achieved. Jackscrews may not always bepresent in all brackets of this type in which case the alternator isrotated about the hinge by use of a lever, typically a wooden stick, andis then fastened by means of a simple bracket and locking fastenerdesigned for that function. In either case the alternator functions asboth the power producing component of the electrical system and thetensioner for the automotive belt that passes over the alternator pulleyto the corresponding drive pulley, typically the engine crankshaftpulley. In certain engines, typically large diesels, an internallycoupled auxiliary drive shaft is equipped with a pulley that used todrive the alternator instead of the crankshaft pulley.

Although effective as a means of mounting the alternator and applyingtension to the drive belt, the J180 standard, having only three mountingpoints, leaves a large portion of the alternator cantilevered. With onlythree mounting lugs, the alternator is subjected to ‘whipping’ about thecantilevered portion which in turn magnifies the effects ofacceleration. Typically these destructive forces are found in bothgasoline and diesel engine applications but are most severe duringstartup of a diesel engine. Violent accelerations are also encounteredwhen the vehicle is subjected to sudden changes in direction, forexample, when hitting a pothole or other similar road hazard. The effectof these forces is to greatly reduce the life expectancy of analternator.

Recent advances in automotive belt engineering has led to thedevelopment of the automatic belt tensioner assemblies, that through theuse of an integral torsion spring, apply the required tension to thebelt thereby eliminating the need for the alternator to function as thebelt tensioner. In this arrangement the alternator lugs are hard mountedto a fixed bracket eliminating the need for a hinge and jack screw.Utilizing automatic belt tensioners has been beneficial in that correctbelt tension is always correctly applied but destructive g forces arestill observed in alternators using the J-180 hinge mount and thevariations utilizing three point mounting lugs since the portion of thealternator without a mounting lug is still subjected to whipping.

In an attempt to further reduce observed destructive forces, the Societyof Automotive Engineers (SAE) issued the Pad Mount AlternatorSpecification Proposal as a method to fastened alternators to engines(SAE document 2002-01-1282). The Pad Mount Alternator SpecificationProposal includes four specification versions, 2-1 through 2-4. 2-1 and2-4 have yet to gain wide acceptance and are intended for future use,whereas 2-2 and 2-3 have gained general acceptance by heavy-duty enginemanufacturers with alternators now being built to the proposedstandards. As will be described later, the Pad Mount alternator utilizesfour mounting lugs that hard mount the alternator to the engine block. Avariation of the J180 mount that includes a fourth mounting lug has alsobeen developed in an attempt to reduce destructive forces. In eithercase the alternator is hard mounted to the engine at four points. TheSAE Pad Mount standard as well as the J180 four point variant physicallylimits overall alternator diameter due to the fixed distances betweenmounting lugs used to fasten the alternator. Presently with overalldiameter being limited, the only effective means of increasingalternator output in a Pad Mount alternator is to increase the overallaxial length. This approach limits output to proportional increases withaxial length. It is very desirable then to develop methods of increasingalternator output while conforming to the predefined geometry imposed bythe SAE Pad Mount standard or for that matter, any four point mountalternator.

The rotating portion of a permanent magnet alternator comprises a rotorwith permanent magnets affixed thereto. In a given application in whichthe overall diameter of the alternator is limited, one means tosignificantly increase output is to increase the overall length of thestator. As discussed in the Lafontaine et al. application, as the rotorin this type of alternator is open-ended, it is in effect cantileveredand subject to deflection when exposed to severe radial loads. Thereforethe effective length for this type of alternator is limited by theamount of radial load the rotor can resist to prevent the permanentmagnets from clashing with the stator. While a permanent magnet rotorcan be designed to resist most loads, practical limits in terms of sizeand overall weight tend to make this approach impractical beyond certainlengths. It is desirable, therefore, to design a permanent magnetmachine in which the output is substantially increased but not limitedby rotor length.

There has been over time a steady increase in demand to power electricaltools remotely from the power grid. This need is acutely felt by fieldservice personnel tasked with repairing equipment in areas where accessto line-level voltages such as 110 VAC is impractical or completelyunavailable. One method utilized to solve this problem is through theuse of a generator set or, ‘gen-set’ to produce the AC power required byhand drill, radial saws and diagnostic equipment etc. A drawback to thismethod lies in the intense maintenance required by gen-sets as well asthe inconvenience of carrying a large heavy piece of equipment notdirectly connected to the work done by field service personnel. On theother hand, if an under-hood alternator were capable of delivering boththe vehicle system DC power and AC power for external uses, it wouldeliminate the cost and burden of having a generator set. Whenconsidering a single alternator to produce, for example, 12 VDC vehiclepower and 110 VAC power, inefficiencies inherent in either boosting thevoltage to 110 if the alternator is optimized to produce 12 VDC orconversely to step down to 12 V DC if the alternator is optimized toproduce 110 VAC become problematic. Therefore it would be a particularadvantage to produce an alternator capable of multiple electricaloutputs for independent output voltages or current configurationsoptimized for a particular task. Specifically what output voltage rangeoptimized for the 12 VDC and a second independent voltage rangeoptimized for the 110 VAC.

The effects of magnetic fringing are well known and can be utilized toincrease power of a permanent magnet machine. In a permanent magnetalternator, constraining the total available axial length for a givenapplication imparts constraints to the alternator's axial stator length.This is because in addition to the stator fitting within the alternator,the front and rear end plates, the rotor, and necessary clearances forall turns must all also share the same limited axial length. Inpermanent magnet machines, an opportunity to extend the length of themagnet beyond both stator faces is possible without impacting theoverall length of the alternator. The magnetic fringing fields createdin this approach would extend beyond the stator and intercept thewinding end turns that also extend beyond the stator. The result is fluxinteracting with the windings that extend beyond the stator face whichin turn produces more power for a given length of stator. It would bedesirable then to design an alternator that utilizes magnetic fringingas a means to increase power for a fixed length of stator.

Permanent magnet machines tend to demonstrate an undesirable coggingeffect. The cogging effect is a direct result of a permanent magnetalternators' geometry in which magnets are radially disposed equallyabout the rotor, alternating both north and south poles and creating agap between each magnet. The stator comprises teeth and slots arematched to the geometry of the magnets. At rest, the magnetic fieldproduced by the permanent magnets results in a force that predisposesthe magnets to align directly over corresponding teeth on the stator. Asthe rotor begins to spin, the magnetic field produced by the permanentmagnets creates a resistance to rotation as the potential energy of theassembly is increased. As rotation continues potential energy reachesits maximum when the permanent magnets are aligned midway in the gapbetween adjacent stator teeth. From the midway point, further rotationproduces an acceleration that ends when the magnets are again aligneddirectly over the adjacent teeth on the stator. This deceleration andsubsequent acceleration produces the cogging effect observed inpermanent magnet alternators. It is important to note that the neteffect of that cycle is a zero net effect on energy used to rotate thealternator. The cogging of permanent magnet alternators produces severalundesirable characteristics. Two of these effects are merely aesthetic:the first, a high-pitched sound not unlike a siren is produced; thesecond is the inability to freely spin the alternator due to resistanceproduced by the magnetic field of the permanent magnets. Sinceconventional Lundell alternators spin freely in the absence of anexcitation field, it is perceived that the permanent magnet alternatoris not functioning properly. The third and more deleterious effect isfound in larger permanent magnet alternators in which the accelerationand deceleration of cogging produces vibrations that over time canprematurely wear down alternator components. That same acceleration anddeceleration also produces undesirable forces on the drive belt spinningthe alternator, shortening its useful life. The Lafontaine et al.application describes reducing cogging through the use of a skewedstator. As noted in the Lafontaine et al. application one possible meansof fastening a skewed stator is through the use of a hold down ring.

Due to the nature of its geometry, a hold down ring and its fastenersprotrude into the central core, possibly negatively impacting airflow.To maintain adequate cooling fluid flow, it would be beneficial toreduce obstructions that would impede that flow. It would therefore bebeneficial to produce a means of fastening a skewed stator withoutnegatively impacting airflow.

SUMMARY OF THE INVENTION

The present invention provides a particularly advantageous machine forconverting between mechanical and electrical energy. Certain embodimentsprovide for improved alternators that operate within the limitationsimposed by the SAE Pad Mount standard.

Various aspects of the invention provide a means of significantlyincreasing the output of permanent magnet alternators while addressingthe issues of radial loading applied to a permanent magnet alternatorrotor.

Another aspect of the invention allows for the production of power intwo discrete voltages, and in an alternative embodiment, at least oneoutput of the alternator is direct current and another output isalternating current.

In applications where diameter and overall axial length are limited, anaspect of this invention allows for a marked increase in outputcapability without increasing axial length through the use of magneticfringing.

One aspect of the invention offers an effective means of mounting askewed stack that eliminates or reduces cogging that is present in apermanent magnet machine without negatively impacting airflow.

One aspect of the invention reduces cogging by radially offsettingopposing magnets of a dual rotor permanent magnet machine.

One aspect of the invention includes a power conversion apparatuscomprising: a shaft, a first stator, a second stator, a first rotor anda diametrically opposed second rotor. The shaft, stators, and rotorcasings may be coaxially disposed with the rotor casings mounted on theshaft. The first and second stators respectively include at least onewinding. The first rotor further comprises a first plurality ofpermanent magnets coupled to the first rotor and disposed proximate tothe first stator, separated from the first stator by a firstpredetermined gap distance, such that relative motion of the firststator and first rotor causes magnetic flux from the magnets tomagnetically interact with the first stator winding. Also, the secondrotor further comprises a second plurality of permanent magnets coupledto the second rotor and disposed proximate to the second stator,separated from the second stator by a second predetermined gap distance,such that relative motion of the second stator and second rotor causesmagnetic flux from the magnets to magnetically interact with the secondstator winding. The respective first and second plurality of permanentmagnets have a respective predetermined length beyond a respectivepredetermined first and second stator face lengths.

Another aspect of the present invention comprises a cooling system fordirecting coolant flow into thermal contact with at least one of thewinding and magnets. The cooling system generates sufficient coolantflow through'a predetermined flow path at and above a predeterminedspeed to dissipate heat generated and maintains a temperature of themagnets below a predetermined destructive level. The disposition of atleast one of a first and second stator slots and respective permanentmagnets is skewed by a predetermined amount relative to the axis of thefirst and second stator. Also, the radial position of the slots at thefirst core side face is offset from the radial position of the slots atthe second core side face. In one embodiment, the shaft has apredetermined diameter and includes shaft tapered portions disposedbetween the ends of the shaft at predetermined positions relative to thefirst and second stators. The diameter of the shaft tapered portionsvary in accordance with a predetermined taper from a minimum diameter toa predetermined maximum diameter greater than the shaft predetermineddiameter. The first and second rotors include a hub and a centralthrough-bore having the predetermined taper corresponding to a taper ofat least one shaft tapered portion of the shaft. The diameter of thetapered through-bore varies in accordance with the predetermined taperfrom a minimum through-bore diameter greater than the shaftpredetermined diameter to a predetermined maximum through-bore diameter.The first and second rotors hub are disposed with the shaft journaledand extending through the hub through-bore, with the shaft taperedportion received in the through-bore with interior surface of thethrough bore and exterior surface of the shaft tapered portion in matingcontact, wherein cooperation of the tapered first and second rotor boreis in surface contact with the'shaft tapered portion positions the firstand second rotors both axially and radially with respect to the shaftand first and second stators, coupling the first and second rotors tothe shaft for rotation therewith. In one embodiment, the first andsecond rotors and shaft may comprise an integral unit. The first rotormay be mounted on the first endplate; and the first stator is mountedfor rotation relative to the first endplate.

In another embodiment, the shaft is rotatably coupled to the firstendplate. The first and second rotors comprise endcaps coupling acylindrical casing to the shaft; the casing and endcaps comprising anintegral unit.

In one aspect of the present invention the cooling system furthercomprises at least a first passageway through the first end plate influid communication with the predetermined flow path. The cooling systemcoolant may be air, and the cooling system further includes a forced airsupply disposed to move air through the first endplate passageway, andthe predetermined flow path. The forced air supply comprises a fanasynchronous with respect to rotation of the first stator. In anotherembodiment, the cooling system further comprises at least a passagewaythrough a first stator core and a first passageway through the firstrotor in fluid communication with the first stator core passageway.

In one embodiment, the cooling system further comprises a fan mountedfor rotation with the first rotor disposed to move coolant through thefirst stator core passageway. The stator winding includes end turns bentinto the path of coolant flow through the first stator core passageway.Additionally, the cooling system further comprises a deflector surfacedisposed between the first stator and first rotor to direct coolant flowfrom the first stator passageway into thermal contact with winding endturns. Another embodiment includes a second end plate, wherein: thesecond rotor is mounted on the second endplate; and the second stator ismounted for rotation relative to the second endplate. The shaft may berotatably coupled to the second endplate.

The cooling system may further comprise at least a second passagewaythrough the second end plate in fluid communication with thepredetermined flow path.

In another embodiment, the cooling system coolant is air, and thecooling system further includes a forced air supply disposed to move airthrough the second endplate passageway, and the predetermined flow path.The forced air supply may comprise a fan asynchronous with respect torotation of the second stator. The cooling system may further compriseat least a passageway through a second stator core and a passagewaythrough the second rotor in fluid communication with the second statorcore passageway. Also, the cooling system may further comprise a fanmounted for rotation with the second rotor disposed to move coolantthrough the second stator core passageway. The second stator windingincludes end turns bent into the path of coolant flow through the secondstator core passageway. Additionally, the cooling system furthercomprises a deflector surface disposed between the second stator andsecond rotor to direct coolant flow from the second stator passagewayinto thermal contact with winding end turns. In an alternativeembodiment, the cooling system further comprises a rotor deflectordisposed between the first and second rotors. An additional embodimentmay include a second endplate, and an outer casing, wherein: the firstand second rotor casings, first and second stator cores, and outercasing are concentric with the shaft; the shaft is rotatably coupled tothe first and second endplates; the second rotor is mounted on thesecond end plate; and the first and second stator is coupled to theshaft for rotation therewith between the first and second endplates andwithin the outer casing.

The cooling system may comprise a passageway through the first andsecond stator core and a passageway through the first and second rotorin fluid communication with the first and second stator core passageway.The first and second rotor passageway may be disposed such that coolantflow is directed through a first end plate passageway, into thermalcontact with the first stator first winding end turns, through the firststator core passageway, into thermal contact with the first statorsecond winding end turns, into thermal contact with the second statorfirst winding end turns, through the second stator core passageway, intothermal contact with the second stator second winding end turns, througha second end plate passageway; and into thermal contact with the firstand second magnets. Another embodiment includes respective tie rodscooperating with the first and second end plates, compressing the firstand second end plates against the outer casing; the first and secondendplates, outer casing, and tie rods cooperating to maintain alignmentof the shaft, first and second rotors and first and second stators. Thecoolant is air and the cooling system may include at least one forcedair supply disposed to move air through the first and second endplatepassageway, and the first and second stator core passageways. The forcedair supply may comprise at least one electric fan. The electric fans maybe mounted on the first and second endplates. In an alternativeembodiment, the forced air supply comprises at least one fan disposed torotate with the shaft.

Additionally, the first rotor and first stator pairing and second rotorand second stator pairings may comprise independent electrical outputs.The independent outputs may be configured to respectively provide adirect current and an alternating current. For instance, the first rotorand stator pairing and second rotor and stator pairing are configured toprovide an output voltage range optimized for 12 VDC and a secondindependent voltage range optimized for 110 VAC.

In an alternative embodiment, the face length of the magnets areconfigured to produce magnetic fringing stators. Also, the opposingmagnets may be configured radially offset to reduce cogging. Thelaminations of the first and second stators may be configured to beskewed to reduce cogging.

In an alternative embodiment the first and second stators include aplurality of windings, the end turns of such windings extendingoutwardly beyond the core by varying distances to present a lattice-likestructure in the coolant flow path. The end turns extend outwardlybeyond the core peripheral portion side faces to provide spaces betweenthe end turns and core peripheral portion side faces, wherebydissipation of heat generated in the winding is facilitated. In oneembodiment the first and second rotors, first and second stators,cooperate as a compact high power alternator for a vehicle.Alternatively, the first and second rotors and first and second stators,cooperate as a compact high power alternator to retrofit existingvehicles.

Also, the design of the first rotor and diametrically opposed secondrotor aids in resisting apparatus deformation due to acceleration. Thedesign of the first rotor and diametrically opposed second rotor reducesthe length of the moment arm of the apparatus wherein deformation of theplurality of rotors is decreased.

An alternative embodiment of the present invention includes a powerconversion apparatus comprising: a shaft, a first stator, a secondstator, a first rotor and a diametrically opposed second rotor. Theshaft, stators, and rotor casings are coaxially disposed with the rotorcasings mounted on the shaft. The first and second stators include atleast one winding. The first rotor includes a first plurality ofpermanent magnets disposed proximate to the first stator, separated fromthe first stator by a predetermined gap distance, such that relativemotion of the first stator and first rotor causes magnetic flux from themagnets to magnetically interact with the first stator winding. Also,the second rotor includes a second plurality of permanent magnetsdisposed proximate to the second stator, separated from the secondstator by a predetermined gap distance, such that relative motion of thesecond rotor and second stator causes magnetic flux from the magnets tomagnetically interact with the second stator winding. The respectivepermanent first and second plurality of magnets have a predeterminedlength beyond a predetermined first and second stators individual facelengths. Additionally, there may be four lugs that couple the apparatusto a surface. The disposition of at least one of the first and secondstator slots and respective permanent magnets is skewed by apredetermined amount relative to the axis of the first and secondstator; and wherein the first rotor and stator pairing and second rotorand stator pairing comprise independent output voltages. Theseindependent output voltages may comprise a direct current and analternating current. For instance, the first rotor and first statorpairing and second rotor and second stator pairings are configured toprovide an output voltage range optimized for 12 VDC and a secondindependent voltage range optimized for 110 VAC.

It is to be understood that the descriptions of this invention hereinare exemplary and explanatory only and are not restrictive of theinvention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe figures of the appended drawings, wherein like designations denotelike elements.

FIG. 1A is a front view of an existing embodiment of a Pad Mountalternator as reference for the present invention. FIG. 1A includes acut-away view along line B-B.

FIG. 1B is a top view of the Pad Mount alternator of FIG. 1A.

FIG. 1C is a rear view of the Pad Mount alternator of FIG. 1A. (View C-Cin FIG. 1B).

FIG. 1D is a schematic sectional view (taken along line DD in FIG. 1B)of the Pad Mount alternator of FIGS. 1A and 1B.

FIG. 1E is a schematic sectional view (taken along line EE in FIG. 1B)of the Pad Mount alternator of FIGS. 1A and 1B.

FIG. 1F is a detail view (taken along circle FF in FIG. 1E) of the PadMount alternator of FIGS. 1A and 1B.

FIG. 1G is a schematic sectional view (taken along line AA in FIG. 1A)of the Pad Mount alternator of FIGS. 1A and 1B.

FIG. 1H is a schematic sectional view (taken along line AA in FIG. 1A)of the Pad Mount alternator of FIGS. 1A and 1B illustrating a largerdiameter rotor.

FIG. 1I is a schematic sectional view (taken along line AA in FIG. 1A)of the Pad Mount alternator of FIGS. 1A and 1B illustrating an axiallylonger rotor.

FIG. 2A is a front view of the first embodiment of a Pad Mountalternator in accordance with the present invention illustrating amethod of increasing output utilizing two diametrically opposed butunified rotors. (FIG. 2A includes a cut-away view along line G-G).

FIG. 2B is a top view of the Pad Mount alternator of FIG. 2A.

FIG. 2C is a rear view of the alternator of FIG. 2A (View I-I in FIG.4B).

FIG. 2D is a section view of the alternator of FIG. 2B (taken along lineJ-J).

FIG. 2E is a schematic sectional view (taken along line H-H in FIG. 2A)of the Pad Mount alternator of FIGS. 2A and 2B.

FIG. 3A is a front view of a second embodiment of an alternator inaccordance with the present invention that maximizes output utilizingtwo diametrically opposed but unified rotors of equal diameters andlengths. FIG. 3A includes a cut-away view taken along-line K-K.

FIG. 3B is a top view of the alternator of FIG. 3A.

FIG. 3C is a rear view of the alternator of FIG. 3A (View M-M of FIG.3B).

FIG. 3D is a schematic sectional view (taken along line N-N in FIG. 3A)of the alternator of FIGS. 3A and 3B.

FIG. 3E is a schematic sectional view (taken along line L-L in FIG. 3A)of the alternator of FIGS. 3A and 3B.

FIG. 3F is a schematic sectional view (taken along line L-L in FIG. 3A)of the alternator of FIGS. 3A and 3B that maximizes output utilizing twodiametrically opposed but unified rotors of equal diameters and unequallengths, illustrating stator and rotor groups of unequal length.

FIGS. 4A-4C is simplified schematics illustrating the effects of radialloading on alternator rotors (Alternators in FIG. 1A-1I).

FIGS. 4D-4F are simplified schematics illustrating the effects of radialloading on diametrically opposed but unified rotor of equal diameter andlength (Alternator in FIG. 3A-3D).

FIGS. 4G-4H are simplified schematics illustrating the effects of radialloading on diametrically opposed but unified rotors of unequal diameters(Alternator in FIG. 2A-2E).

FIGS. 4I-4J are simplified schematics illustrating the effects of radialloading on diametrically opposed but unified rotors of equal diametersbut unequal lengths (Alternator in FIG. 3F).

FIG. 5A is a front view of a fifth embodiment of an alternator inaccordance with the present invention that maximizes output for a givendiameter utilizing two discrete rotors FIG. 5A includes a cut-away viewtaken along line 0-0.

FIG. 5B is a top view of the alternator of FIG. 5A.

FIG. 5C is a rear view of the alternator of FIG. 5A taken along line Q-Q(FIG. 5C includes a cutaway view taken along line T-T).

FIG. 5D is a section view of the alternator of FIG. 5B taken along lineR-R (FIG. 5D includes a cut-away view taken along line U-U).

FIG. 5E is a partial section view of the alternator of FIG. 5B takenalong line S-S (FIG. 5E includes a cut-away view taken along line V-V.

FIG. 5F is a schematic sectional view (taken along line P-P in FIG. 5A)alternator of FIGS. 5A and 5B.

FIG. 5G is a schematic sectional view (taken along line P-P in FIG. 5A)of the Pad Mount alternator of FIGS. 5A and 5B with the option of twoclosely spaced discrete rotors.

FIG. 6A is a front view of a sixth embodiment of a Pad Mount alternatorin accordance with the present invention that maximizes output utilizingmagnetic fringing.

FIG. 6B is a schematic sectional view (taken a long line, X-X in FIG.6A) illustrating magnet overhang.

FIG. 7A-7G are detailed views detailing a method to fasten skewedpermanent magnet alternator stators.

FIG. 8A is a detailed view of a dual rotor with offset magnets.

FIG. 8B is a detailed cut away view of the dual rotor in FIG. 8A takealong line Y-Y.

DESCRIPTION OF THE EMBODIMENTS

Referring now to FIGS. 1A-1G, as described by Lafontaine et al., tomaximize power output in a permanent magnet machine, it is desirable tomaximize certain dimensions such as the diameter of a stator and rotor.Put another way, it would be desirable to maximize the diameter of acircle described about the outer radius of the teeth 158 of the core 156given size, housing, and mounting constraints. This diameter is referredto herein as the air gap diameter Dag (see FIG. 1F). As discussed above,the Society of Automotive Engineers, (SAE) has proposed four mountingstandards, versions 2-1 through 2-4, suitable for vehicle applications.The mounting hole pattern shown in FIG. 1B with its radial spreadbetween bolts 103 and 107 and between bolts 105 and 109, set at 190.0mm, and axial spread between bolts 103 and 105 and between bolts 107 and109, set at 126.3 mm conforms to SAE Pad Mount version 2-3 and iscommonly found in truck applications. FIG. 1A shows mounting surface 111of alternator 100 contacting mounting bracket 101 which maintains radialclearance required for the alternator, as proposed by SAE as a minimumof 70.0 mm but typically 102 mm is utilized. Unless otherwise indicatedherein, all dimensions are provided in inches.

When considering mounting bolts 103, 105, 107 and 109 in Pad Mountapplications there are two current methods of increasing power. Thefirst is to increase the diameter of the rotor such that its overalllength fits between the axial spread of the mounting bolts to avoidinterference as best seen in FIG. 1H. The second method is to increasethe overall length of the rotor by selecting a rotor diameter thatavoids interference with the radial spread of the mounting bolts as bestseen in FIG. 1I. Of the two methods, increasing diameter is moredesirable since the increase in power is proportional to the square ofthe diameter whereas increasing rotor length only yields an increase inpower proportional to length.

Conventional alternator manufacturers have chosen to design alternatorswith the overall stator and armature diameters within the radial spreadas proposed by the SAE. This is in part due to the increase the armatureof a conventional alternator adds to the overall diameter, i.e. a modestincrease in power for a conventional alternator translates to anunacceptable increase in diameter. As a result the approach has been toincrease the axial length rather than diameter. FIG. 1G shows witnessline 113 illustrating the maximum air gap diameter from the central axisof the alternator that could be attained in an alternator whenrestricted by the radial spread of the mounting bolts. In reality themaximum attainable radius for the rotor is further reduced due tomaterial of endplate 126 surrounding each mounting bolt. Although thepreferred method of increasing output is to increase the overall air gapdiameter, the possible overall axial length is limited thereby limitingpotential output. Conversely, increasing the axial length of the rotorto improve output is limited due to the diminished air gap diameter. Itwould be desirable therefore to incorporate both increased diameter andincreased axial length in a single Pad Mount alternator to maximizepotential output.

Referring now to FIGS. 1A-1G an apparatus for converting betweenmechanical and electrical energy, e.g., alternator 100, which conformsto SAE proposed pad mount standard version 2-3, comprises: a shaft 110,preferably including a tapered projecting portion 112 and a threadedportion 114 (best seen in FIG. 1G); a rotor 116; a stator 118; a frontendplate 120; a front bearing 122; a rear endplate 126; a rear shaftretaining rings 128; a rear bearing 130; an outer casing 132 andrespective tie rods 134. Rotor 116 is mounted on shaft 110 for rotationwith the shaft. Stator 118 is closely received within rotor 116,separated from rotor 116 by a small air gap AG. Front endplate 120,front bearing 122, rear bearing 130, rear endplate 126, outer casing 132and tie rods 134 cooperate as a support assembly to maintain alignmentof shaft 110, rotor 116, and stator 118. Shaft 110 is maintained bybearings 122 and 130, which are mounted on front endplate 120 and rearendplate 126, respectively, and rotatably maintain and align shaft 110concentric and perpendicular with the endplates. Rotor 116 is mountedfor rotation on shaft 110 and fixed axially by jam nut 124, positivelypositioned by cooperation with tapered shaft portion 112. Rear endplate126 mounts and locates stator 118 so that it is disposed within rotor116 properly aligned with shaft 110 and rotor 116. Outer casing 132 hasend faces perpendicular to its axis (is preferably cylindrical) and isdisposed between front endplate 120 and rear endplate 126. Tie rods 134;compress endplates 120 and 126 against outer casing 132, keeping thecomponents squared and in alignment.

In a typical automotive alternator application, pulley 136, fan 138 andnut 140 are mounted on the end of shaft 110. Power from an engine (notshown) is transmitted through an appropriate belt drive (not shown) topulley 136, and hence shaft 110. Torque so applied to the shaft 110 inturn causes rotor 116 to rotate about stator 118. Rotor 116 generates amagnetic field, which interacts with windings on stator 118. As themagnetic field intercepts the windings, an electrical current isgenerated, which is provided to a suitable load. The induced current istypically applied to a bridge rectifier, sometimes regulated, andprovided as an output. In some instances, the regulated output signal isapplied to an inverter to provide an AC output.

As best seen in FIG. 1G, rotor 116 preferably comprises an endcap 142, acylindrical casing 144 and a predetermined number (e.g. 8 pairs) ofalternatively poled permanent magnets 146 disposed in the interior sidewall of casing 144.

As best seen in FIG. 1D, rotor endcap 142 is suitably substantiallyopen, including a peripheral portion 131, respective cross-arms 148 anda central rotor hub 150 to provide for connection to shaft 110.Respective air passageways 152 are provided through endcap 142, boundedby peripheral portion 131, adjacent cross arms 148, and central hub 150.Central rotor hub 150 includes a through-bore 154 having a predeterminedtaper (e.g. 1 in. per foot) corresponding to that of shaft portion 112.In assembly, shaft 110 is journaled through bore 154, such that shafttapered portion 112 is received in bore 154 just forward of threadedshaft portion 114. Threaded shaft portion 114 cooperates with jam nut124 to positively locate rotor 116 on shaft 110. In general, thethickness of crossarms 148 is suitably chosen to be as thin as possible(to minimize weight and material cost) while still capable ofwithstanding expected loads, suitably in the range of ⅜ in. to ⅝ inch atits thinnest point. Since rotor casing 144 is, in effect, cantileveredfrom endcap 142, the necessary thickness is proportional to the lengthof casing 144. Rotor hub 150, in the vicinity of bore 154, is suitablythick enough to provide adequate surface contact with tapered shaftportion 112, suitably on the order of 1½ inch.

Stator 118 suitably comprises a core 156 and conductive windings 170.Core 156 suitably comprises laminated stack of thin sheets of softmagnetic material, e.g. non-oriented, low loss (lead free) steel, thatare cut or punched to the desired shape, aligned and joined (e.g. weldedor epoxied together in a precision jig to maintain the separatelaminations in alignment). As best seen in FIGS. 1E and 11F, core 156 isgenerally-cylindrical, with an axially crenellated outer peripheralsurface, i.e., includes a predetermined number of teeth 158 and slots160. The tooth alignment is typically axial but under certain controlsystems requiring the acquisition of waveform timing and/or to eliminatethe cogging effect found in axially aligned laminations, the laminationscan be progressively skewed of a prescribed tooth offset from end to end(preferably but not limited to an offset of one tooth) as will beexplained later, a method of securing a skewed stator without negativelyimpacting air flow will be explained. Core 156 is preferablysubstantially open, with a central aperture 162, and suitably includescrossarms 164 and axial through-bores 166 to facilitate mounting to rearendplate 126 using mounting bolts 168. As will be described later radialslots can be utilized to mount the lamination stack to optimize air flowthrough central aperture 162

Windings 170, formed of a suitably insulated electrical conductor,preferably varnished copper motor wire, are provided on core 156, woundthrough a respective slot 160, outwardly along the side face of core 156around a predetermined number of teeth 158, then back through anotherslot 160.

In assembly, stator 118 is disposed coaxially with rotor 116, and isclosely received within interior cavity of rotor 116. As will beexplained, rear endplate 126 mounts and locates stator 118 so that it isproperly aligned within internal chamber of rotor 116. The peripheralsurface of stator core 156 is separated from the interior surface ofmagnets 146 by a small predetermined air gap AG (best seen in FIG. 1F).Air gap AG is suitably in the range of 20 to 40 thousands of an inch,and in the embodiments of FIGS. 1A-1I on the order of 30 thousands of aninch, e.g., 31 thousands of an inch. Accordingly, the inner diameter ofcasing 144, magnets 146, and outer diameter of stator core 156 arepreferably held to close tolerances to maintain alignment. It isimportant that rotor 116 and stator 118 be carefully aligned, anddisplacement of the elements from their normal positions due to externalforces on the alternator held below a threshold value.

As noted above, alignment of shaft 110, rotor 116, and stator 118achieved by a bearing structure comprising front endplate 120, frontbearing 122, rear bearing 130, rear endplate 126, outer casing 132 andtie rods 134. Bearings 122 and 130, in effect, provide respective pointsof rotatable connection between shaft 110 and the bearing structure.Bearings 122 and 130, and hence shaft 110, are disposed concentric andperpendicular with endplates 120 and 126, respectively. Rotor 116 ispreferably positively positioned with respect to shaft 110 throughcooperation of tapered rotor hub through bore 154 and tapered shaftportion 112. Stator 118 is located relative to and aligned with shaft110, and hence rotor 116, by rear endplate 126. The alignment ofendplates 120 and 126 is maintained by outer casing 132 and tie rods134.

Front endplate 120 is suitably generally cylindrical, including: acentrally disposed hub 174, including a coaxial aperture 176 with aperipheral portion 178 including respective (e.g. 4) counter bored holes180 disposed at predetermined radial distances from the center ofaperture 176, distributed at equal angular distances, to receive tierods 134; and respective (e.g., 4) crossarms 182 connecting peripheralportion 178 to hub 174, and defining respective air passages 184. Frontendplate 120 is dimensioned and machined to high tolerance (e.g. plus orminus 0.0008 TYP for aperture 176, 0.005 TYP for other features, such astie rod hole 180 patterns, outer case shoulder, mounting hole patterns),suitably formed of metal e.g. cast aluminum, and should be sufficientlystrong to withstand the rotational loads created by the turning of shaft110 and rotor 116, as well as side loading that occurs as a result ofthe belt pulling on pulley 136. Front bearing 122 is closely received inbearing sleeve 186. Front endplate 120 and bearing sleeve 186 which isused to distribute the stresses produced by the loads transferred fromshaft 110 to bearing 122. Bearing sleeve 186 locates front bearing 122and shaft 110.

Rear endplate 126 carries and locates rear bearing 130, mounts andlocates stator 118. Rear endplate 126 suitably includes a steppedcentral hub 188 having a forward reduced diameter portion 190 andcentral aperture 192 there through, and a generally cylindrical rearwardgoing outer peripheral portion 194, preferably having the same outerprofile as front endplate 120, connected to hub 188 by respectivecrossarms 145. Respective tapped holes 196 are provided cylindricalouter peripheral portion 194, at the same radial distance from centerand angular dispositions as counter bored holes 180 in front endplate120. A predetermined number of tapped holes 196 (e.g. 4) correspondingto stator crossarm bores 166 are provided in the stepped surface ofprojection 188. The outer diameter of reduced diameter portion 190 issubstantially equal to (but slightly less than) the diameter of theconcentric radial locating features 198 on crossarms 164, so that rearendplate portion 190 may be closely received within the concentricradial locating features 198 on crossarms 164 of stator 118. Rearendplate 126 is dimensioned and machined to high tolerance (e.g. plus orminus 0.0008 TYP for central aperture 192, 0.005 TYP for other features,such as tapped holes 196 patterns, outer case shoulder, mounting holepatterns), suitably formed of metal e.g. cast aluminum. Rear bearing 130is closely received within aperture 192 of rear endplate hub 188 andthus centers shaft 110. Stator 118 is mounted on hub 188, with reduceddiameter hub portion 190 received within the concentric radial locatingfeatures 198 on crossarms 164 of stator 118 and the stator rear sidewallagainst the hub step. Respective bolts 168 journaled through bores 166and secured in tapped holes 196, secure stator 118 to rear endplate 126.Stator 118 is thus positively located and aligned relative to shaft 110.Since endplates 120 and 126 are held in alignment with each other byouter casing 132 and tie rods 134, shaft 110 (and tapered portion 112)is held in alignment with endplates 120 and 126 by bearings 122 and 130,and stator 118 is positively positioned and aligned with shaft 110 byendplate 126, the positive positioning and a centering of rotor 116 onshaft 110 also provides relative positioning and alignment between rotor116 and stator 118.

For a given stator length, increasing the diameter of a stator and rotorof a permanent magnet machine, more specifically, increasing the air gapdiameter Dag produces a significant increase in output (output increasesby the square of the diameter).

Referring now to FIG. 1H, increasing the air gap diameter significantlyincreases output of alternator 100 without changing any components otherthan increasing the diameter of the rotor and stator. Alternator 147,which also conforms to SAE proposed pad mount standard version 2-3,comprises: a shaft 110, preferably including a tapered projectingportion 112 and a threaded portion 114 (best seen in FIG. 1H); a rotor115; a stator 123; a front endplate 120; a front bearing 122; a rearendplate 126; a rear shaft retaining rings 128; a rear bearing 130; anouter casing 132 and respective tie rods 134.

Rotor 115 is mounted on shaft 110 for rotation with the shaft 110. Rotor115 has a larger diameter then that of rotor 116 and extends beyondwitness line 113. Like rotor 116, rotor 115 is comprised of an endcap117, a cylindrical casing 119 and a predetermined number (e.g. 8 pairs)of alternatively poled permanent magnets 121 disposed in the interiorside wall of casing 119. Rotor endcap 117 is suitably substantiallyopen, including a peripheral portion 137, respective cross-arms (notshown) and a central rotor hub 139 to provide for connection to shaft110. Respective air passageways 152 are provided through endcap 117,bounded by peripheral portion 137, adjacent cross arms (not shown), andcentral hub 139. Central rotor hub 139 includes a through-bore 141having a predetermined taper (e.g. 1 in. per foot) corresponding to thatof shaft portion 112. In assembly, shaft 110 is journaled through bore141, such that shaft tapered portion 112 is received in bore 141 justforward of threaded shaft portion 114. Threaded shaft portion 114cooperates with jam nut 124 to positively locate rotor 115 on shaft 110.In general, the thickness of the crossarms (not shown) is suitablychosen to be as thin as possible (to minimize weight and material cost)while still capable of withstanding expected loads, suitably in therange of ⅜ in. to ⅝ inch at its thinnest point. Since rotor casing 119is, in effect, cantilevered from endcap 117, the necessary thickness isroughly proportional to the length of casing 119. Rotor hub 139, in thevicinity of bore 141, is suitably thick enough to provide adequatesurface contact with tapered shaft portion 112, suitably on the order of1½ inch. In all physical and functional respects, rotor 115 is similarto rotor 116 of alternator 100

There is a corresponding increase in the diameter of stator 123 to matchthat of rotor 115 which increases the air gap diameter Dag. Stator 123suitably comprises a core (not shown) and conductive windings 170. Thestator core suitably comprises laminated stack of thin sheets of softmagnetic material, e.g. non-oriented, low loss (lead free) steel, thatare cut or punched to the desired shape, aligned and joined (e.g. weldedor epoxied together in a precision jig to maintain the separatelaminations in alignment). The core is generally cylindrical, with anaxially crenellated outer peripheral surface, i.e., includes apredetermined number of teeth and slots (reference FIG. 1E) and ispreferably substantially open, with a central aperture 127, and suitablyincludes crossarms (not shown) and axial through-bores 129 to facilitatemounting to rear endplate 126 using mounting bolts 168. Windings 170,formed of a suitably insulated electrical conductor, preferablyvarnished copper motor wire, are provided on the core (not shown), woundthrough a respective slot (not shown), outwardly along the side face ofcore (not shown) around a predetermined number of teeth (not shown),then back through another slot (not shown).

In assembly, stator 123 is disposed coaxially with rotor 115, and isclosely received within interior cavity of rotor 115. The peripheralsurface of stator core (not shown) is separated from the interiorsurface of magnets 121 by a small predetermined air gap AG (see, e.g.,FIG. 1F). Air gap AG is suitably in the range of 20 to 40 thousands ofan inch, and in the embodiments of FIGS. 1A-1I on the order of 30thousands of an inch, e.g., 31 thousands of an inch. Accordingly, theinner diameter of casing 119, magnets 121, and outer diameter of stator123 are preferably held to close tolerances to maintain alignment. It isimportant that rotor 116 and stator 118 be carefully aligned, anddisplacement of the elements from their normal positions due to externalforces on the alternator held below a threshold value.

Stator 123 is mounted on hub 188, with reduced diameter hub portion 190received within the concentric radial locating features 198 on crossarms(not shown) of stator 118 and the stator rear sidewall against the hubstep. Respective bolts 168 journaled through bores 129 and secured intapped holes 196, secure stator 123 to rear endplate 126. Stator 123 isthus positively located and aligned relative to shaft 110. Sinceendplates 120 and 126 are held in alignment with each other by outercasing 132 and tie rods 134, shaft 110 (and tapered portion 112) is heldin alignment with endplates 120 and 126 by bearings 122 and 130, andstator 123 is positively positioned and aligned with shaft 110 byendplate 126, the positive positioning and a centering of rotor 115 onshaft 110 also provides relative positioning and alignment between rotor116 and stator 118. In all respects, physical and functional, stator 123is similar to stator 118 of alternator 100.

The second method of improving output in a permanent magnet machine isachieved by increasing the axial length of both the rotor and stator.Lengthening the rotor and stator is a less desirable method since theincrease in output varies linearly in relationship to increases inlength. However, in certain applications increasing length of the rotorand stator may be the only viable method of increasing output. Amongother drawbacks to increasing length, as described by Lafontaine et al.,the length of the rotor in applications such as engine mounting ispractically limited by the forces exerted on the alternator from acantilevered installation.

Referring now to FIG. 1I; Alternator 133, which also conforms to SAEproposed pad mount standard version 2-3, comprises: a shaft 167,preferably including a tapered projecting portion 112 and a threadedportion 114 (best seen in FIG. 1H); a rotor 135; a stator 137; a frontendplate 120; a front bearing 122; a rear endplate 149; a rear shaftretaining rings 128; a rear bearing 130; an outer casing 132 andrespective tie rods 134.

The outer diameter of rotor 135 is designed such that clearance ismaintained between rotor casing 175 and rear endplate 149. Rotor 135 ismounted on shaft 167 for rotation with the shaft 110. Rotor 135 iscomprised of an endcap 177, a cylindrical casing 175 and a predeterminednumber (e.g. 8 pairs) of alternatively poled permanent magnets 173disposed in the interior side wall of casing 175. Rotor endcap 177 issuitably substantially open, including a peripheral portion 179,respective crossarms (not shown) and a central rotor hub 181 to providefor connection to shaft 167. Respective air passageways 183 are providedthrough endcap 177, bounded by peripheral portion 179, adjacent crossarms (not shown), and central hub 181. Central rotor hub 181 includes athrough-bore 183 having a predetermined taper (e.g. 1 in. per foot)corresponding to that of shaft portion 112. In assembly, shaft 167 isjournaled through bore 183, such that shaft tapered portion 112 isreceived in bore 183 just forward of threaded shaft portion 114.Threaded shaft portion 114 cooperates with jam nut 124 to positivelylocate rotor 135 on shaft 167. In general, the thickness of thecrossarms (not shown) is suitably chosen to be as thin as possible (tominimize weight and material cost) while still capable of withstandingexpected loads, suitably in the range of ⅝ in. to 53/4 inch at itsthinnest point due to the increased length. Since rotor casing 175 is,in effect, cantilevered from endcap 177, the necessary thickness isroughly proportional to the length of casing 177. Rotor hub 181, in thevicinity of bore 183, is suitably thick enough to provide adequatesurface contact with tapered shaft portion 112, suitably on the order of1½ inch. In all physical and functional respects, rotor 135 is similarto rotor 116 of alternator 100.

Rear endplate 149 carries and locates rear bearing 130, mounts andlocates stator 137. Rear endplate 149 includes a rearward extension 151to accept the increased length of stator 137 and suitably includes astepped central hub 153 having a forward reduced diameter portion 155and central aperture 157 there through, and a generally cylindricalrearward going outer peripheral portion 159, preferably having the sameouter profile as front endplate 120. Respective tapped holes 161 areprovided cylindrical outer peripheral portion 159, at the same radialdistance from center and angular dispositions as counter bored holes 180in front endplate 120. A predetermined number of tapped holes 163 (e.g.4) corresponding to stator 137 crossarm bores 165 are provided in thestepped surface of projection 153. The outer diameter of reduceddiameter portion 155 is substantially equal to (but slightly less than)the diameter of the concentric radial locating features (not shown) oncrossarms (not shown), so that rear endplate portion 155 may be closelyreceived within the concentric radial locating features (not shown) oncrossarms (not shown) of stator 137. Rear endplate 149 is dimensionedand machined to high tolerance (e.g. plus or minus 0.0008 TYP forcentral aperture 157, 0.005 TYP for other features, such as tapped holes163 patterns, outer case shoulder, mounting hole patterns), suitablyformed of metal e.g. cast aluminum. Rear bearing 130 is closely receivedwithin aperture 157 of rear endplate hub 153 and thus centers shaft 167.Stator 137 is mounted on hub 153, with reduced diameter hub portion 155received within the concentric radial locating features (not shown) oncrossarms (not shown) of stator 137 and the stator rear sidewall againstthe hub step. Respective bolts 169 journaled through bores 165 andsecured in tapped holes 163, secure stator 137 to rear endplate 149.Stator 137 is thus positively located and aligned relative to shaft 167.Since endplates 120 and 149 are held in alignment with each other byouter casing 132 and tie rods 134, shaft 167 (and tapered portion 112)is held in alignment with endplates 120 and 149 by bearings 122 and 130,and stator 137 is positively positioned and aligned with shaft 167 byendplate 149, the positive positioning and a centering of rotor 135 onshaft 167 also provides relative positioning and alignment between rotor135 and stator 137.

Stator 137, with its corresponding increase in the length to match thatof rotor 135, suitably comprises a core (not shown) and conductivewindings 170. The stator core suitably comprises laminated stack of thinsheets of soft magnetic material, e.g. non-oriented, low loss (leadfree) steel, that are cut or punched to the desired shape, aligned andjoined (e.g. welded or epoxied together in a precision jig to maintainthe separate laminations in alignment). The core is generallycylindrical, with an axially crenellated outer peripheral surface, i.e.,includes a predetermined number of teeth and slots (reference FIG. 1E)and is preferably substantially open, with a central aperture 171, andsuitably includes crossarms (not shown) and axial through-bores 165 tofacilitate mounting to rear endplate 149 using mounting bolts 169.Windings 170, formed of a suitably insulated electrical conductor,preferably varnished copper motor wire, are provided on the core (notshown), wound through a respective slot (not shown), outwardly along theside face of core (not shown) around a predetermined number of teeth(not shown), then back through another slot (not shown).

In assembly, stator 137 is disposed coaxially with rotor 135, and isclosely received within interior cavity of rotor 135. The peripheralsurface of stator core (not shown) is separated from the interiorsurface of magnets 173 by a small predetermined air gap AG (referenceFIG. 1F). The air gap AG is suitably in the range of 20 to 40 thousandsof an inch, and in the embodiments of FIGS. 1I on the order of 30thousands of an inch, e.g., 31 thousands of an inch. Accordingly, theinner diameter of rotor casing 175, magnets 173, and outer diameter ofstator 137 are preferably held to close tolerances to maintainalignment. It is important that rotor 135 and stator 137 be carefullyaligned, and displacement of the elements from their normal positionsdue to external forces on the alternator held below a threshold value.

As described above, alternators conforming to the proposed SAE Pad Mountstandard are limited by the mounting bolt hole pattern. Manufacturerscan either increase the air gap diameter Dag, fitting the rotor andstator between the axial mounting bolts or utilize a significantlysmaller diameter rotor and stator and staying between the radial spreadof the mounting bolts. Referring now to FIGS. 2A-2E that illustrate amethod of dramatically increasing alternator output by combiningdiametrically opposed rotor casings while still maintainingcompatibility with the SAE proposed Pad Mount Standard.

Alternator 200 has many similar features found in alternator 100; ashaft 202, preferably including a tapered projecting portion 112 and athreaded portion 114; a jam nut 124; front end plate 204; a frontbearing 122; a bearing sleeve 176; a rear bearing 130; a rear shaftretaining ring 128; an outer casing 132 and respective tie rods 134.Rear end plate 206 has been extended to except rear stator 217 and rotorportion 209.

Rotor 201, like rotor 116, has support plate 203, analogous to rotorendplate 134; but is centrally located with two diametrically opposedrotor casing portions 207; and 209; of unequal diameters. Rotor casingportion 209 is of a reduced diameter sufficient to clear mounting bolts105 and 109. Front endplate 206, unlike front endplate 120, mounts andlocates front stator 215 as well as carrying and locating front bearing122.

Stators 215 and 217 suitably comprise cores 288 and 290 respectively andconductive windings 272 and 254 respectively. Cores 288 and 290 suitablycomprises laminated stack of thin sheets of soft magnetic material, e.g.non-oriented, low loss (lead free) steel, that are cut or punched to thedesired shape, aligned and joined (e.g. welded or epoxied together in aprecision jig to maintain the separate laminations in alignment). Asbest seen in FIG. 2D, cores 288 and 290 are generally cylindrical, withan axially crenellated outer peripheral surface, i.e., includes apredetermined number of teeth 158 and slots 160. Both stator 215 and 217are preferably substantially open, with stator 215 having a centralaperture 266 and suitably includes crossarms 224, radial locatingfeature 222 and axial through-bores 220 to facilitate mounting to frontendplate 204 using mounting bolts 246 and stator 217 having a centralaperture 262 and suitably includes crossarms 286, radial locatingfeature 284 and axial through-bores 240 to facilitate mounting to rearendplate 248 using mounting bolts 246. As will be described later radialslots can be utilized to mount the lamination stack to optimize air flowthrough the central apertures 262 and 266

Windings 254 and 272, formed of a suitably insulated electricalconductor, preferably varnished copper motor wire, are provided on cores288 and 290, wound through a respective slot 160, outwardly along theside face of cores 288 and 290 around a predetermined number of teeth158, then back through another slot 160.

In assembly, stators 215 and 217 are disposed coaxially with rotor 201,and are closely received within interior cavities of rotor 201. As willbe explained, rear endplate 206 mounts and locates rear stator 217 andfront endplate 204 mounts and locates front stator 215 so that it isproperly aligned within internal chambers of rotor 201. The peripheralsurface of stator cores 288 and 290 are separated from the interiorsurface of magnets 211 and 213 by a small predetermined air gap diameterDag (best seen in FIG. 1F).

Front endplate 204 suitably includes a stepped central hub 208 having aforward reduced diameter portion 210 and central aperture 212 therethrough, and a generally cylindrical outer peripheral portion 214connected to hub 208 by respective crossarms 252. Respective counterbored holes 216 are provided cylindrical outer peripheral portion 214. Apredetermined number of tapped holes 218 (e.g. 4) corresponding tostator crossarm bores 220 are provided in the stepped surface ofprojection 208. The outer diameter of reduced diameter portion 210 issubstantially equal to (but slightly less than) the diameter of theconcentric radial locating features 222 on crossarms 224, so that frontendplate portion 210 may be closely received within the concentricradial locating features 222 on crossarms 224 of stator 215. Frontbearing sleeve 176 is closely received within counter bore 226 of frontendplate hub 208 and thus centers shaft 202. Stator 215 is mounted onhub 208, with reduced diameter hub portion 210 received within theconcentric radial locating features 222 on crossarms 224 of stator 215and the stator front sidewall against the hub step. Respective bolts 293journaled through bores 220 and secured in tapped holes 218, securestator 215 to front endplate 204. Stator 215 is thus positively locatedand aligned relative to shaft 202.

Rear endplate 206, to accommodate the increase in axial length as aresult of the addition of rear rotor portion 209 and stator 217, hascylindrical extension 248 that carries and locates rear bearing 130,mounts and locates stator 217. Cylindrical extension 248 must be ofadequate strength to support the increased stress as a result ofmounting stator 217. Rear endplate 206, has a generally cylindricalrearward going outer peripheral portion 234, preferably having the sameouter profile as front endplate 204, cylindrical extension 248 suitablyincludes a stepped central hub 208 connected by respective crossarms 244having a forward reduced diameter portion 230 and central aperture 232there through. Respective tapped holes 236 are provided cylindricalouter peripheral portion 234, at the same radial distance from centerand angular dispositions as counter bored holes 216 in front endplate204. A predetermined number of tapped holes 238 (e.g. 4) correspondingto stator crossarm bores 240 are provided in the stepped surface ofprojection 228. The outer diameter of reduced diameter portion 230 issubstantially equal to (but slightly less than) the diameter of theconcentric radial locating features 284 on crossarms 286, so that rearendplate reduced portion 230 may be closely received within theconcentric radial locating features 284 on crossarms 286 of stator 217.Rear bearing 130 is closely received within aperture 232 of rearendplate hub 228 and thus centers shaft 202. Stator 217 is mounted onhub 228, with reduced diameter hub portion 230 received within theconcentric radial locating features 284 on crossarms 286 of stator 217and the stator rear sidewall against the hub step. Respective bolts 246journaled through bores 240 and secured in tapped holes 238, securestator 217 to rear endplate 206. Stator 217 is thus positively locatedand aligned relative to shaft 202.

Rotor 201 is mounted on shaft 202 for rotation with the shaft. Stators215; and 217 are closely received within rotor 201, separated from rotor201 by a respective air gaps AG. Front endplate 204, bearing sleeve 186,front bearing 122, rear bearing 130, rear endplate 206, outer casing 132and tie rods 134 cooperate as a support assembly to maintain alignmentof shaft 202, rotor 201, and stators 215 and 217. Shaft 202 ismaintained by bearings 122 and 130, which are mounted on front endplate204 and rear endplate 206, respectively, and rotatably maintain andalign shaft 202 concentric and perpendicular with the endplates. Rotor201 is mounted for rotation on shaft 202, positively positioned bycooperation with tapered shaft portion 112. Front endplate 204 mountsand locates stator 215 that it is disposed within rotor 201 properlyaligned with shaft 202 and rotor 201. Rear endplate 206 mounts andlocates stator 217 so that it is disposed within rotor 201 properlyaligned with shaft 202 and rotor 201. Outer casing 132 has end facesperpendicular to its axis (is preferably cylindrical) and is disposedbetween front endplate 204 and rear endplate 206. Tie rods 134; compressendplates 204 and 206 against outer casing 132, keeping the componentssquared and in alignment.

Referring to FIG. 2E, a cooling airflow 278 entering alternator 200 isdirected over stator windings 254 (preferably through loosely wrappedfront-side and rear-side end turns 256 and 258 respectively) byemploying a cooling system comprising air passageways 260 in rear endplate 206 (bounded by adjacent rear end plate crossarms 244, outerportion 248, and hub 228), stator 217 central aperture 262, rotor airpassages 264, over stator windings 272 (preferably through looselywrapped front-side and rear-side end turns 274 and 276 respectively)stator 215 central aperture 266 and front end plate air passages 268.Air flow 278 entering rear end plate air passage way 260 is directed toimpinge on windings 254 (rear-side end turns 258), Air exiting statorcentral aperture 262 is directed to impinge on windings 254 (front-sideend turns 256), by virtue of suitable relative disposition orcontouring, or, as in the embodiment of FIG. 2E, cooperation with ashaft mounted rear deflector 270. Air exiting rotor air passages 264 isdirected to impinge on windings 272 of stator 215 through rear-side endturns 276. After passing over rear-side end turns 276 is then directedto stator 215 central aperture 266 by use of rotor deflector 282 thenover front-side end turns 274 then through front endplate 204 airpassageway 268. An asynchronous forced air supply, e.g., electric fan asoutlined by Lafontaine et al., may be mounted to the rear of end plate206 to enhance air flow. In the preferred embodiment, centrifugal fan138 is mounted for rotation with shaft 202 between pulley 136 and frontend plate 204. The cross sections, contours (turns and edges) andrelative dispositions of the various air passageways are preferablychosen to minimize decreases in air velocity, and maximize airflow overend turns 258, 256 of stator 217 and end turns 274, 276 of stator 215.

More specifically, cooling air, generally indicated by arrows 278 isintroduced into alternator 200 through end plate air passageways 260.Airflow 278 impinges upon rear end turn 258. Airflow 278 then splitsinto respective streams 280 and 282. After exiting the end turns 258,air stream 280 flows through stator 217 central aperture 262, impingesupon rear shaft deflector 270, is then directed through the front-sideloosely wrapped end turns 256, air flow 280 then enters rotorpassageways 264, impinges on end turns 276 of stator 215 then with thecooperation of rotor deflector 282, is directed into stator 215 centralaperture 266 and then exits alternator 200 through air passageways 268in front end plate 204. Air stream 282, after exiting rear-side endturns 258, flows between the outside of rotor casing portion 209 andthen between rotor portion 207 and the inside of cylindrical portion 248and outer case 132 then impinges on front side end turns 274 of stator215 then exits alternator 200 through air passageways 268 in front endplate 204. Air stream 282 provides cooling of magnets 213, 211 and frontside end turns 274. Air stream 280 provides cooling for end turns 258,256 and 276.

As described above, the use of diametrically opposed rotor casingsoffers an opportunity to significantly increase alternator outputwithout subjecting the rotor to excessive deformation if the entirelength of the rotor casing were otherwise cantilevered. In the case ofan SAE pad mount alternator, the use of a reduced rotor diameter at oneend of a diametrically opposed rotor casing to adequately clear mountingbolts is of particular advantage. In applications in which the diameterof the rotor can be maximized for the entire length of the rotor,maximum output is achieved for that application. Alternator 300, due tothe increased length and singular axial diameter, could not be used inan application conforming to the proposed SAE Pad Mount standard butwould also be well suited in a variety of other mounting applicationssuch as the J180 SAE standard or other similar mounting pattern.

Referring now to FIGS. 3A-3E, Alternator 300 has many similar featuresfound in alternator 200 but most notably the diametrically opposedrotors are of equal diameters. Alternator 300 has a shaft 302,preferably including a tapered projecting portion 112 and a threadedportion 114; a jam nut 124; front end plate 304; a front bearing 122;rear endplate 306; a rear bearing 130; a rear shaft retaining ring 128;an outer casing 308 and respective tie rods 310. Rotor 326 has supportplate 328 that is centrally located in rotor casing 330 with twodiametrically opposed rotor casing portions 332; and 334 that are ofequal diameters.

Stators 340 and 342 suitably comprise cores 312 and 314 respectively andconductive windings 316 and 318 respectively. Cores 312 and 314 suitablycomprises laminated stack of thin sheets of soft magnetic material, e.g.non-oriented, low loss (lead free) steel, that are cut or punched to thedesired shape, aligned and joined (e.g. welded or epoxied together in aprecision jig to maintain the separate laminations in alignment). Asbest seen in FIG. 3D, cores 312 and 314 are generally cylindrical, withan axially crenellated outer peripheral surface, i.e., includes apredetermined number of teeth 158 and slots 160. Both stator 340 and 342are preferably substantially open, with stator 340 having a centralaperture 320 and suitably includes crossarms 349, radial locatingfeature 351 and axial through-bores 322 to facilitate mounting to frontendplate 304 using mounting bolts 359 and stator 342 having a centralaperture 324 and suitably includes crossarms 353, radial locatingfeature 355 and axial through-bores 393 to facilitate mounting to rearendplate 306 using mounting bolts 313.

Windings 316 and 318, formed of a suitably insulated electricalconductor, preferably varnished copper motor wire, are provided on cores312 and 314, wound through a respective slot 160, outwardly along theside face of cores 312 and 314 around a predetermined number of teeth158, then back through another slot 160.

In assembly, stators 340 and 342 are disposed coaxially with rotor 326,and are closely received within interior cavity of rotor 326. As will beexplained, rear endplate 306 mounts and locates rear stator 342 andfront endplate 304 mounts and locates front stator 340 so that it isproperly aligned within internal chambers of rotor 326. The peripheralsurface of stator 340 and 342 are separated from the interior surface ofmagnets 336 and 338 by a small predetermined air gap AG (see, e.g., FIG.1F).

Front endplate 304 suitably includes a stepped central hub 397 having aforward reduced diameter portion 317 and central aperture 395 therethrough, and a generally cylindrical outer peripheral portion 321connected to hub 323 by respective crossarms 325. Front endplate airpassageways 331 are bounded by outer peripheral portion 321, hub 323 andcrossarms 325. Respective counter bored holes 327 are providedcylindrical outer peripheral portion 321. A predetermined number oftapped holes 344 (e.g. 4) corresponding to stator crossarm bores 322 areprovided in the stepped surface of projection 397. The outer diameter ofreduced diameter portion 317 is substantially equal to (but slightlyless than) the diameter of the concentric radial locating features 351on crossarms 349, so that reduced diameter portion 317 may be closelyreceived within the concentric radial locating features 351 on crossarms349 of stator 340. Front bearing sleeve 186 is closely received withincounter bore 346 of front endplate hub 397 and thus centers shaft 302.Stator 340 is mounted on hub 397; with reduced diameter hub portion 317received within the concentric radial locating features 351 on crossarms349 of stator 340 and the stator front sidewall against the hub step.Respective bolts 359 journaled through bores 322 and secured in tappedholes 344, secure stator 340 to front endplate 304. Stator 340 is thuspositively located and aligned relative to shaft 302.

Rear endplate 306 carries and locates rear bearing 130, mounts andlocates stator 342. Rear endplate 306 suitably includes a steppedcentral hub 348 having a forward reduced diameter portion 350 andcentral aperture 352 there through, and a generally cylindrical outerperipheral portion 354, preferably having the same outer profile asfront endplate 304, connected to hub 348 by respective crossarms 356.Outer peripheral portion 354, crossarms 356 and hub 348 form rearendplate 306 air passageways 358. Respective tapped holes 360 areprovided in cylindrical outer peripheral portion 354, at the same radialdistance from center and angular dispositions as counter bored holes 327in front endplate 304. A predetermined number of tapped holes 362 (e.g.4) corresponding to stator crossarm bores 393 are provided in thestepped surface projection of hub 348. The outer diameter of reduceddiameter portion 350 is substantially equal to (but slightly less than)the diameter of the concentric radial locating features 355 on crossarms 353 of stator 342, so that reduced diameter portion 350 may beclosely received within the concentric radial locating features 355 oncross arms 353 of stator 342. Rear bearing 130 is closely receivedwithin aperture 352 of rear endplate hub 348 and thus centers shaft 302.Stator 342 is mounted on hub 348, with reduced diameter hub portion 350received within the concentric radial locating features 355 on crossarms353 of stator 342 and the stator rear sidewall against the hub step.Respective bolts 313 journaled through bores 393 and secured in tappedholes 362, secure stator 342 to rear endplate 306. Stator 342 is thuspositively located and aligned relative to shaft 302.

Rotor 326 is mounted on shaft 302 for rotation with the shaft. Stators340 and 342 are closely received within rotor 326, separated from rotor326 by a small air gap AG (see, e.g., FIG. 1F). Front endplate 304,bearing sleeve 186, front bearing 122, rear bearing 130, rear endplate306, outer casing 308 and tie rods 310 cooperate as a support assemblyto maintain alignment of shaft 302, rotor 326, and stators 340 and 342.Shaft 302 is maintained by bearing sleeve 186, bearings 122 and 130,which are mounted on front endplate 304 and rear endplate 306,respectively, and rotatably maintain and align shaft 302 concentric andperpendicular with the endplates 304 and 306. Rotor 326 is mounted forrotation on shaft 302, positively positioned by cooperation with taperedshaft portion 112. Front endplate 304 mounts and locates stator 340 sothat it is disposed within rotor portion 332 properly aligned with shaft302 and rotor 326. Rear endplate 306 mounts and locates stator 342 sothat it is disposed within rotor portion 334 properly aligned with shaft302 and rotor 326. Outer casing 308 has end faces perpendicular to itsaxis (is preferably cylindrical) and is disposed between front endplate304 and rear endplate 306. Tie rods 310; compress endplates 304 and 306against outer casing 308, keeping the components squared and inalignment.

Referring again to FIG. 3E, a cooling airflow is directed over statorwindings 318 of stator 342 (preferably through loosely wrapped rear-sideand front-side end turns 364 and 366 respectively) by employing acooling system comprising air passageways 358 in rear end plate 306,stator 342 central aperture 324, rotor air passages 329, stator 340central aperture 320 and front end plate air passages 331. Air enteringrear end plate air passage way 358 is directed to impinge on rear-sideend turns 364 of windings 318, Air exiting stator central aperture 324is directed to impinge on windings 318 (front-side end turns 366), byvirtue of suitable relative disposition or contouring, or, as in theembodiment of FIG. 3E, cooperation with a shaft mounted rear deflector333. Air exiting rotor air passages 329 is directed to impinge onwindings 316 of stator 340 (preferably through loosely wrapped rear-sideand front-side end turns 335 and 337 respectively). After passing overrear-side end turns 335 is then directed to stator 340 central aperture320 by use of rotor deflector 339 then over front-side end turns 337then through front endplate 304 air passageway 331. An asynchronousforced air supply, e.g., electric fan as outline by Lafontaine et al.,may be mounted on the back of rear end plate 306 to enhance air flow. Inthe preferred embodiment, centrifugal fan 138 is mounted for rotationwith shaft 302 between pulley 136 and front end plate 304. The crosssections, contours (turns and edges) and relative dispositions of thevarious air passageways are preferably chosen to minimize decreases inair velocity, and maximize airflow over end turns 364, 366 of stator 342and end turns 335, 337 of stator 342.

More specifically, cooling air, generally indicated by arrows 341 isintroduced into alternator 300 through rear end plate air passageways358. Airflow 341 impinges upon rear end turn 364. Airflow 341 thensplits into respective streams 343 and 345. After exiting the end turns364, air stream 343 flows through stator 342 central aperture 324,impinges upon rear shaft deflector 333, is directed through thefront-side loosely wrapped end turns 366, rotor passageways 329,impinges on end turns 335 of stator 340 is, with cooperation of rotordeflector 339, directed into stator 340 central aperture 320 thenpartial impinges on end turns 337 and then exits alternator 300 throughair passageways 331 in front end plate 304. Air stream 345, afterexiting rear-side end turns 364, flows between the outside of rotorcasing 303 and the inside of outer casing 308 then impinges on frontside end turns 337 of stator 340 then exits alternator 300 through airpassageways 331 in front end plate 304. Air stream 345 provides coolingfor magnets 336, 338 and end turns 364 and 337. Air stream 343 providescooling for end turns 364, 366, 335 and 337.

The demand is high for a single device to provide multiple electricaloutputs for use with possible multiple output voltages and/or currentconfigurations, for example a single apparatus configured to provide 12VDC to power vehicle systems and 110 VAC to power equipment such as sawsand drills for use in remote locations. The alternator stators describedin FIGS. 3A-3E can be wound independently to produce voltage ranges moreclosely matching the desired application. For example stator 342 can beoptimized to closely match the 12 V DC vehicle system power with stator340 optimized to more closely match the 110V AC power requirements. Thedisadvantage in taking this approach with two equally sized stators isfor example, the excess capability stator 340 has in powering the 12 VDCvehicle system. Modern trucks typically require 80 amps or less to powervehicle systems. With stators 340 and 342 equally sized, it would not beunexpected to have stator 340 capable of producing 250 to 350 amps ofpower. In that particular configuration, 170 to 270 amps of power would,in essence, go to ‘waste’. Therefore it would be beneficial in certainapplications to have different stator lengths in order to optimizeoutput. Specifically stator 342 could be shortened to more closely matchthe 80 amp vehicle requirement and stators 340 could be lengthened todeliver the maximum amperage possible for the 110 V AC system.

Referring now to FIG. 3F, Alternator 357 has a shaft 309, preferablyincluding a tapered projecting portion 112 and a threaded portion 114; ajam nut 124; front end plate 304; a front bearing 122; rear endplate306; a rear bearing 130; a rear shaft retaining ring 128; an outercasing 308 and respective tie rods 310. Rotor 368 has support plate 370that is located offset from center in rotor casing 372 with twodiametrically opposed rotor casing portions 374 and 376 having equaldiameters. Rotor portion 374 and stator 382 are longer than rotorportion 376 and stator 384.

Stators 382 and 384 suitably comprise cores and conductive windings 392and 394 respectively. Stators 382 and 384 cores suitably compriseslaminated stack of thin sheets of soft magnetic material, e.g.non-oriented, low loss (lead free) steel, that are cut or punched to thedesired shape, aligned and joined (e.g. welded or epoxied together in aprecision jig to maintain the separate laminations in alignment).Stators 382 and 384 cores are generally, cylindrical, with an axiallycrenellated outer peripheral surface, i.e., includes a predeterminednumber of teeth and slots (not shown, reference FIG. 3D). Both stator382 and 384 are preferably substantially open, with stator 382 having acentral aperture 396 and suitably includes crossarms (not shown,reference FIG. 3D), radial locating feature (not shown, reference FIG.3D) and axial through-bores 398 to facilitate mounting to front endplate304 using mounting bolts 301 and stator 384 having a central aperture303 and suitably includes crossarms (not shown, reference FIG. 3D),radial locating feature (not shown, reference FIG. 3D) and axialthrough-bores 305 to facilitate mounting to rear endplate 306 usingmounting bolts 307.

Windings 392 and 394, formed of a suitably insulated electricalconductor, preferably varnished copper motor wire, are provided on coresof stator 382 and 384 respectively, wound through respective slots,outwardly along the side face of cores around a predetermined number ofteeth, then back through another slot.

In assembly, stators 382 and 384 are disposed coaxially with rotor 368;and are closely received within interior cavity of rotor 368. As will beexplained, rear endplate 306 mounts and locates rear stator 384 andfront endplate 304 mounts and locates front stator 382 so that it isproperly aligned within internal chambers of rotor 368. The peripheralsurface of stator cores 382 and 384 are separated from the interiorsurface of magnets 378 and 380 by a small predetermined air gap AG (see,e.g., FIG. 1F).

Front endplate 304, as previously described, suitably includes a steppedcentral hub 397 having a forward reduced diameter portion 317. Apredetermined number of tapped holes 344 (e.g. 4) corresponding tostator crossarm bores 398 are provided in the stepped surface ofprojection 397. Reduced diameter portion 317 is substantially equal to(but slightly less than) the diameter of the concentric radial locatingfeatures (not shown, reference FIG. 3D) on crossarms (not shown,reference FIG. 3D), so that front endplate portion 304 may be closelyreceived within the concentric radial locating features (not shown,reference FIG. 3D) on crossarms (not shown, reference FIG. 3D) of stator382. Front bearing sleeve 186 is closely received within counter bore346 of front endplate hub 397 and thus centers shaft 309. Stator 382 ismounted on hub 397, with reduced diameter hub portion 317 receivedwithin the concentric radial locating features (not shown, referenceFIG. 3D) on crossarms (not shown, reference FIG. 3D) of stator 382 andthe stator front sidewall against the hub step. Respective bolts 301journaled through bores 398 and secured in tapped holes 344, securestator 382 to front endplate 304. Stator 382 is thus positively locatedand aligned relative to shaft 309.

Rear endplate 306 mounts and locates stator 384. Rear endplate 306suitably includes a stepped central hub 348 having a forward reduceddiameter portion 350. A predetermined number of tapped holes 362 (e.g.4) corresponding to stator crossarm bores 305 are provided in thestepped surface projection of hub 348. The outer diameter of reduceddiameter portion 350 is substantially equal to (but slightly less than)the diameter of the concentric radial locating features (not shown,reference FIG. 3D) on cross arms (not shown, reference FIG. 3D) ofstator 382, so that reduced diameter portion 350 of rear endplate 306may be closely received within the concentric radial locating features(not shown, reference FIG. 3D) on the cross arms (not shown, referenceFIG. 3D) of stator 382. Rear bearing 130 is closely received withinaperture 352 of rear endplate hub 348 and thus centers shaft 309. Stator384 is mounted on hub 348, with reduced diameter hub portion 350received within the concentric radial locating features (not shown,reference FIG. 3D) on crossarms (not shown, reference FIG. 3D) of stator384 and the stator rear sidewall against the hub step. Respective bolts307 journaled through bores 305 and secured in tapped holes 362, securestator 382 to rear endplate 306. Stator 382 is thus positively locatedand aligned relative to shaft 309.

Rotor 326 is mounted on shaft 309 for rotation with the shaft. Stators382 and 384 are closely received within rotor 368, separated from rotor368 by a small air gap AG (see, e.g., FIG. 1F). Front endplate 304,bearing sleeve 186, front bearing 122, rear bearing 130, rear endplate306, outer casing 308 and tie rods 310 cooperate as a support assemblyto maintain alignment of shaft 309, rotor 368, and stators 382 and 384.Shaft 309 is maintained by bearings 122 and 130, which are mounted onfront endplate 302 and rear endplate 306, respectively, and rotatablymaintain and align shaft 309 concentric and perpendicular with theendplates 304 and 306. Rotor 368 is mounted for rotation on shaft 309,positively positioned by cooperation with tapered shaft portion 112.Front endplate 304 mounts and locates stator 384 so that it is disposedwithin rotor portion 374 properly aligned with shaft 309 and rotor 368.Rear endplate 306 mounts and locates stator 384 so that it is disposedwithin rotor portion 376 properly aligned with shaft 309 and rotor 368.Outer casing 308 has end faces perpendicular to its axis (is preferablycylindrical) and is disposed between front endplate 304 and rearendplate 306. Tie rods 310; compress endplates 304 and 306 against outercasing 308, keeping the components squared and in alignment.

Referring again to FIG. 3F, a cooling airflow is directed over statorwindings 394 of stator 384 (preferably through loosely wrapped rear-sideand front-side end turns 311 and 313 respectively) by employing acooling system comprising air passageways 358 in rear end plate 306,stator 384 central aperture 303, rotor air passages 315, stator 382central aperture 396 and front end plate air passages 331. Air enteringrear end plate air passage way 358 is directed to impinge on rear-sideend turns 311 of windings 394, Air exiting stator central aperture 303is directed to impinge on windings 394 (front-side end turns 313), byvirtue of suitable relative disposition or contouring, or, as in theembodiment of FIG. 3F, cooperation with a shaft mounted rear deflector317. Air exiting rotor air passages 315 is directed to impinge onwindings 392 of stator 382 (preferably through loosely wrapped rear-sideand front-side end turns 319 and 321 respectively). After passing overrear-side end turns 319 is then directed to stator 382 central aperture396 by use of rotor deflector 347 then over front-side end turns 321then through front endplate 304 air passageway 331. An asynchronousforced air supply, e.g., electric fan as outline by Lafontaine et al.,may be mounted on the back of rear end plate 306 to enhance air flow. Inthe preferred embodiment, centrifugal fan 138 is mounted for rotationwith shaft 309 between pulley 136 and front end plate 304. The crosssections, contours (turns and edges) and relative dispositions of thevarious air passageways are preferably chosen to minimize decreases inair velocity, and maximize airflow over end turns 311, 313 of stator 384and end turns 319, 321 of stator 382.

More specifically, cooling air, generally indicated by arrows 341 isintroduced into alternator 357 through rear end plate air passageways358. Airflow 341 impinges upon rear end turn 311. Airflow 341 thensplits into respective streams 343 and 345. After exiting the end turns311, air stream 343 flows through stator 384 central aperture 303,impinges upon rear shaft deflector 317, is directed through thefront-side loosely wrapped end turns 313, rotor passageways 315,impinges on end turns 319 of stator 382 then with cooperation with rotordeflector 347, is directed into stator 382 central aperture 396 thenpartial impinges on end turns 321 and then exits alternator 357 throughair passageways 331 in front end plate 304. Air stream 345, afterexiting rear-side end turns 311, flows between the outside of rotorcasing 372 and the inside of outer casing 308 then impinges on frontside end turns 321 of stator 382 then exits alternator 357 through airpassageways 331 in front end plate 304. Air stream 345 provides coolingof magnets 378, 380 and end turns 311 and 321. Air stream 343 providescooling for end turns 311, 313, 319 and 321.

The embodiments of the invention described in FIGS. 2 and 3 carry withit an ancillary benefit in that deformation of the rotor is greatlyreduced during accelerations due to the nature of the physicalconfiguration of the rotor casing and rotor endplate. As described byLafontaine et al., the maximum length of a rotor is limited by theamount of load the rotor endplate can effectively resist to preventcritical deformation resulting in destructive clashing between magnetsand rotor.

Referring to FIGS. 4A-4C (which have been greatly simplified to improveclarity), In the absence of external forces, rotor 116 of alternator 100is concentric and perpendicular with shaft 110; rotor casing 144 is in anominal normal position (designated by lines 402 and 404) coaxial withshaft 110 and the forward (closest to forward endplate) edge of rotorendcap 142 is in a nominal normal position (designated by line 406)perpendicular to the axis of shaft 110. Components of external forcestypically encountered parallel to the axis of shaft 110 tend to havelittle effect on the disposition of rotor 116; rotor endcap 142 andcooperation of rotor hub (not shown), tapered shaft portion 112, and jamnut (not shown) are sufficiently strong to resist axial movement ordistortion of rotor 116, and, in any event, there is greater toleranceto axial distortions. However, external forces encountered perpendicularto the axis of shaft 110 of sufficient strength will distort rotor 116if not properly account for.

More specifically, rotor 116 has a centroid (center of gravity) 403 thatextends out beyond the conjunction of rotor endcap 142 and shaft 110(indicated a schematically as pivot (cantilever) point 408 creating amoment arm when subjected to accelerations that are perpendicular toshaft 110. This is true as well for those accelerations that are notcompletely perpendicular but which present a perpendicular component ofthe resultant acceleration to shaft 110. When subjected to accelerationsperpendicular to the axis of shaft 110, rotor casing 144 tends to resistdeformation due to its cylindrical shape, however the distortion canmanifested itself in rotor endcap 142. In effect, rotor 116 iscantilevered and in response to perpendicular accelerations, rotor 116,in effect, pivots about pivot point 408. Maximum deflection from thenominal normal position is experienced at the portions of rotor 116farthest from pivot point 408, i.e. the distal (rear) end of casing 144,and the outer periphery of endcap 142 (where endcap 142 joins casing144). If the deflection in the vicinity of magnets 146 exceeds air gapAG, e.g. 31 thousands of an inch, magnets 146 will clash with stator118, causing possibly destructive interference.

For example, as shown in FIG. 4B, in response to an upward acceleration,rotor 116 will in effect pivot downwardly (as shown but exaggerated forclarity, in a clockwise direction). The upward side of rotor casing 144will effectively pivot inwardly towards shaft 110, with the distal enddeflected inwardly from the nominal normal position 402 by an amountgenerally indicated as 410. The upward periphery of endcap 142 similarlymoves to the rear of its nominal normal position 406 by an amountgenerally indicated as 412. Conversely, the distal end of downward sideof rotor casing 144 will be deflected outwardly from the nominal normalposition 402 by an amount generally indicated as 414 and the downwardperiphery of endcap 142 similarly moves forward of its nominal normalposition 406 by an amount generally indicated as 416. Since cylindricalrotor casing 144 tends to maintain its shape, the amount of deflectionof the corresponding upper and lower portions are substantiallyproportional i.e. deflections 410 and 412 are substantially proportionalto deflections 414 and 416, respectively.

Forces from opposite directions will cause mirror image deflections. Forexample, as shown in FIG. 4C, in response to a downward acceleration,rotor 116 will in effect pivot upwardly (as shown, in a counterclockwisedirection). The downward side of rotor casing 144 will effectively pivotinwardly towards shaft 110, with the distal end deflected inwardly fromthe nominal normal position 404 by an amount generally indicated as 418.The downward periphery of endcap 142 similarly moves to the rear of itsnominal normal position 406 by an amount generally indicated as 420.Conversely, the distal end of upward side of rotor casing 144 will bedeflected upwardly from the nominal normal position 402 by an amountgenerally indicated as 422 and the upward periphery of endcap 142similarly moves forward of its nominal normal position 406 by an amountgenerally indicated as 424. Again, since cylindrical rotor casing 144maintains its shape, the amount of deflection of the corresponding upperand lower portions are substantially proportional i.e. deflections 418and 420 are substantially proportional essays to deflections 422 and424, respectively.

As described above, accelerations perpendicular to shaft 110 tend todeflect rotor 116 such that magnets 146 could clash with stator 118 ifthe acceleration is severe enough. The problem of rotor deflectionincreases as the axial length increases, more specifically as the lengthof the moment arm increases. As with any mechanical system, the rotorcan be designed to resist destructive deflections, no matter how severethe acceleration, but in practical terms this would require a rotor withvery thick rotor end plates and casings to resist deflection, veryundesirable in automotive and other applications in which weight is animportant consideration. As was described in FIGS. 3, it is possible todramatically increase the output utilizing diametrically opposed rotorswithout subjecting the rotor to deformation resulting in a clash betweenmagnets and stator.

Referring now to FIGS. 4D-4F (which have been simplified to improveclarity), rotor 326 of alternator 300 is comprised of support plate 328coaxially disposed at the axial center of a single cylindrical rotorcasing 330, forming two diametrically opposed cylindrical casingportions 332 and 334. Cylindrical casing portion 332 has a predeterminednumber (e.g. 8 pairs) of alternatively poled permanent magnets 336disposed in the interior wall of casing portion 332. Cylindrical casingportion 334 as well has a predetermined number (e.g. 8 pairs) ofalternatively poled permanent magnets 338 disposed in the interior wallof casing portion 334. Because rotor support plate 328 of rotor 326 iscentrally located within casing 330 the centroid 403 of rotor 326 islocated at pivot point 408. As the alternator is subjected toaccelerations, rotor casing portion 332 of rotor 326 will tend todeflect counter clockwise (direction 426) about pivot point 408. Rotorcasing portion 334 of rotor 326 will tend to deflect clockwise(direction 428) about pivot point 408. Rotor casing 330 due to itscylindrical shape is very well suited to resist deformation and sincecentroid 403 of rotor 326 is at pivot point 408, loads will tend to betransferred along path 430 down through the body of support plate 328 toshaft 110. Since the forces being transferred through support plate 328do not extend beyond the body of support plate 328, there is no momentarm therefore no significant deformation to rotor 326 occurs.

As was described in regards to FIGS. 2A-2E, a method of dramaticallyincreasing output while conforming to the proposed SAE pad mountstandard was detailed. This rotor configuration also benefits in itsability to resist deformation due to severe acceleration.

Referring now to FIGS. 4G and 4H (which have been simplified to improveclarity), rotor 201 of alternator 200 is comprised of two diametricallyopposed rotors of unequal diameters. Rotor 201 is comprised of supportplate 203 coaxially disposed at the axial center of a dual cylindricalrotor casing 205 forming two diametrically opposed cylindrical casingportions 207 and 209 which is of a lesser diameter. Cylindrical casingportion 207 has a predetermined number (e.g. 8 pairs) of alternativelypoled permanent magnets 211 disposed in the interior wall of casingportion 207. Cylindrical casing portion 209 as well has a predeterminednumber (e.g. 8 pairs) of alternatively poled permanent magnets 213disposed in the interior wall of casing portion 209. Rotor support plate203 of rotor 201 is centrally located within casing 205 but becauserotor portion 207 is of a larger diameter than that of rotor portion 209it has a slightly larger mass which locates centroid 403 of rotor 201slightly to the left of pivot point 408. It's important to note thedifference in mass between rotor portions 207 and 209 is relativelysmall creating a small moment arm during acceleration, much smaller thanthat of alternator 100 and as would be expected, a smaller amount ofdistortion. As alternator 200 is subjected to accelerations, rotorcasing portion 207 of rotor 201 will tend to deflect counter clockwise(direction 426) about pivot point 408. Rotor casing portion 209 of rotor201 will tend to deflect clockwise (direction 428) about pivot point408. Rotor casing 201 due to its cylindrical shape is very well suitedto resist deformation and since centroid 403 of rotor 201 is justslightly left of pivot point 408, loads will tend to be transferred toshaft 110 with only slight deformation to rotor support plate 203 due tothe small moment arm presented.

Optimizing an alternator by utilizing discrete output is beneficial inapplications requiring dual voltage outputs. By producing an alternatorwith stators of different lengths to produce amperage output atdifferent voltages, an optimization is realized. In such applicationsthe rotor support plate can be engineered to sufficiently resist thedeformation caused by the increased centroid length presented duringacceleration.

Referring now to FIGS. 4I and 4J, (which have been greatly simplified toimprove clarity), In the absence of external forces, rotor 368 ofalternator 309 is concentric and perpendicular with shaft 309; rotorcasing 372 is in a nominal normal position (designated by lines 432 and436) coaxial with shaft 309 and the forward (closest to front endplate304) edge of rotor casing 372 is in a nominal normal position(designated by line 438) perpendicular to the axis of shaft 309 and therearward (closest to rear endplate 306) edge of rotor casing 372 is in anominal normal position (designated by line 440) is also perpendicularto the axis of shaft 309. Components of external forces typicallyencountered parallel to the axis of shaft 309 tend to have little effecton the disposition of rotor 368; rotor support plate 370 and cooperationof rotor hub (not shown), tapered shaft portion 112, and jam nut (notshown) are sufficiently strong to resist axial movement or distortion ofrotor 368, and, in any event, there is greater tolerance to axialdistortions. However, external forces encountered perpendicular to theaxis of shaft 309 can be of sufficient strength to distort rotor 368 ifnot properly account for.

More specifically, rotor 368 has a centroid (center of gravity) 403 thatextends out beyond the conjunction of rotor support plate 370 and shaft309 (indicated a schematically as pivot point 408) creating a moment arm(cantilever) due to the unequal lengths, when subjected to accelerationsthat are perpendicular to shaft 309. This is true as well for thoseaccelerations that are not completely perpendicular but which present aperpendicular component of the resultant acceleration to shaft 309. Whensubjected to accelerations perpendicular to the axis of shaft 309, rotorcasing 372 tends to resist deformation due to its cylindrical shape,however the distortion can manifested itself in rotor support plate 370.In effect, rotor 368 is cantilevered and in response to perpendicularaccelerations, rotor 368 pivots about pivot point 408. Maximumdeflection from the nominal normal position is experienced at theportions of rotor 368 farthest from pivot point 408, i.e. the distal(rotor portion 374) end of rotor casing 372. If the deflection in thevicinity of magnets 378 exceeds air gap AG, e.g. 31 thousands of aninch, magnets 378 will clash with stator 382, causing possiblydestructive interference. For example, as shown in FIG. 4J, in responseto an upward acceleration, rotor 368 will in effect pivot downwardly (asshown but exaggerated for clarity, in a counter clockwise direction).The upward side of rotor portion 374 will effectively pivot downwardlyfrom the nominal normal position 432 by an amount generally indicated as442. The downward side of rotor portion 374 will effectively pivotdownwardly from the nominal normal position 434 by an amount generallyindicated as 444. Conversely, the upward side of rotor portion 376 willbe deflected upwardly from the nominal normal position 432 by an amountgenerally indicated as 446, the downward side of rotor portion 376 willbe deflected upwardly from the nominal normal position 432 by an amountgenerally indicated as 448. Since rotor portion 374 is farthest awayfrom pivot point 408, it will see the greatest amount of deflection fora given amount of rotation by rotor 368. Rotor support plate 370 musttherefore be of sufficient strength to resist deformation causingdestructive clashing between magnets 378 and stator 382.

The alternators described in FIGS. 2 and 3, utilizing diametricallyopposed rotor casings with a single rotor support plate is of particularadvantage in terms of both increased output and ability to resistdeformation. Although certainly not as capable in resisting deformationwhen subjected to substantial acceleration, two independent rotors eachconsisting of discrete endplates and rotor casings positioned indiametric opposition on a single shaft can attain similar increases inoutput to that of alternator 300. Since each rotor casing is in essencecantilevered care must be taken to properly engineer and selectmaterials for the rotor and plates that will resist destructivedeformation resulting in rotor magnets clashing with each stator.

Referring now to FIG. 5A-5F, Alternator 500 suitably includes a shaft502 with two tapered projecting portions, 504 and 506 and two threadedportions 508 and 510; two jam nuts 512 and 514; front end plate 516; afront bearing 122; bearing sleeve 186; rear endplate 518, rear shaftretaining rings 128; a rear bearing 130; twin rotors 530 and 532;stators 568 and 570; an outer case 520 contain air flow intake vents 522and respective tie rods 524. Fans 537 and 539, in cooperation with vents522, cool the heat producing components of alternator 500. Twin rotors530 and 532, as best seen in FIG. 5F, both preferably comprise an endcap534 and 536, a cylindrical casing 538 and 540 respectfully and apredetermined number (e.g. 8 pairs) of alternatively poled permanentmagnets 542 disposed in the interior side wall of casing 538 and apredetermined number (e.g. 8 pairs) of alternatively poled permanentmagnets 544 disposed in the interior side wall of casing 540.

As best seen in FIGS. 5D and 5E, rotors 530 and 532 are suitablysubstantially open, including peripheral portions 546 and 548respectfully, and respective cross-arms 550 and 552 and a central rotorhubs 554 and 556 respectfully to provide for connection to shaft 502.Respective air passageways 558 are provided through endcap 534 of rotor530, bounded by peripheral portion 546, adjacent cross arms 550, andcentral hub 554. Respective air passageways 560 are provided throughendcap 536 of rotor 532, bounded by peripheral portion 548, adjacentcross arms 552, and central hub 556. Central rotor hubs 554 and 556include through-bores 562 and 564 respectively having a predeterminedtaper (e.g. 1 in. per foot) corresponding to that of shaft portion 504and 506. In assembly, shaft 502 is journaled through both bores 562 and564, such that shaft tapered portions 504 and 506 are received in bores562 and 564 just forward of threaded shaft portions 508 and 510.Threaded shaft portions 508 and 510 cooperate with jam nuts 514 and 516to positively locate rotors 530 and 532 on shaft 502. As was previouslydescribed, the thickness of crossarms 550 and 552 are suitably chosen tobe as thin as possible (to minimize weight and material cost) whilestill capable of withstanding expected loads.

Stators 568 and 570 suitably comprise cores 583 and 585 and conductivewindings 572 and 574 respectively. Stators 568 and 570 cores suitablycomprises laminated stack of thin sheets of soft magnetic material, e.g.non-oriented, low loss (lead free) steel, that are cut or punched to thedesired shape, aligned and joined (e.g. welded or epoxied together in aprecision jig to maintain the separate laminations in alignment).Stators 568 and 570 cores are generally cylindrical, with an axiallycrenellated outer peripheral surface, i.e., includes a predeterminednumber of teeth 158 and slots 160. Both stator 568 and 570 arepreferably substantially open, with stator 568 having a central aperture576 and suitably includes crossarms 575, radial locating feature 577 andaxial through-bores 578 to facilitate mounting to front endplate 516using mounting bolts 580 and stator 570 having a central aperture 582and suitably includes crossarms 579, radial locating feature 581 andaxial through-bores 584 to facilitate mounting to rear endplate 518using mounting bolts 586.

Windings 572 and 574, formed of a suitably insulated electricalconductor, preferably varnished copper motor wire, are provided on cores583 and 585 of stator 568 and 570 respectively, wound through respectiveslots 160, outwardly along the side face of cores around a predeterminednumber of teeth 158, then back through another slot.

In assembly, stator 568 is disposed coaxially with rotor 530 and isclosely received within interior cavity of rotor 530. As will beexplained, front endplate 516 mounts and locates front stator 568 sothat it is properly aligned within internal chambers of rotor 530 andstator 570 is disposed coaxially with rotor 532 and is closely receivedwithin interior cavity of rotor 532. As will be explained, rear endplate518 mounts and locates rear stator 570 so that it is properly alignedwithin internal chambers of rotor 532. The peripheral surface of stators568 and 570 are separated from the interior surface of magnets 542 and544 respectively by a small predetermined air gap AG (see, e.g., FIG.1F).

Front endplate 516 suitably includes a stepped central hub 592 having aforward reduced diameter portion 594 and central aperture 596 therethrough, and a generally cylindrical outer peripheral portion 598,preferably having the same outer profile as rear endplate 518, connectedto hub 592 by respective crossarms 501. Respective counter bored holes503 are provided cylindrical outer peripheral portion.598. Apredetermined number of tapped holes 553 (e.g. 4) corresponding tostator crossarm bores 578 are provided in the stepped surface of hub592. Reduced diameter portion 594 is substantially equal to (butslightly less than) the diameter of the concentric radial locatingfeatures 577 on crossarms 575 of stator 568, so that front endplateportion 594 may be closely received within the concentric radiallocating features 577 on crossarms 575 of stator 568. Front bearingsleeve 186 is closely received within counter bore 505 of front endplatehub 592 and thus centers bearing 122 and shaft 502. Stator 568 ismounted on hub 592, with reduced diameter hub portion 594 receivedwithin the concentric radial locating features 577 on crossarms 575 ofstator 568 and the stator front sidewall against the hub step.Respective bolts 580 journaled through bores 578 and secured in tappedholes 553, secure stator 568 to front endplate 516. Stator 516 is thuspositively located and aligned relative to shaft 502.

Rear endplate 518 carries and locates rear bearing 130, mounts andlocates stator 570. Rear endplate 518 suitably includes a steppedcentral hub 509 having a forward reduced diameter portion 511 andcentral aperture 513 there through, and a generally cylindrical outerperipheral portion 515, preferably having the same outer profile asfront endplate 516, connected to hub 509 by respective crossarms 517.Respective tapped holes 519 are provided cylindrical outer peripheralportion 515, at the same radial distance from center and angulardispositions as counter bored holes 503 in front endplate 516. Apredetermined number of tapped holes 591 (e.g. 4) corresponding tostator crossarm bores 584 are provided in the stepped surface of hub509. The outer diameter of reduced diameter portion 511 is substantiallyequal to (but slightly less than) the diameter of the concentric radiallocating features 581 on crossarms 579, so that rear endplate portion511 may be closely received within the concentric radial locatingfeatures 581 on crossarms 579 of stator 570. Rear bearing 130 is closelyreceived within aperture 513 of rear endplate hub 509 and thus centersshaft 502. Stator 570 is mounted on hub 509, with reduced diameter hubportion 511 received within the concentric radial locating features 581on crossarms 579 of stator 570 and the stator rear sidewall against thehub step. Respective bolts 586 journaled through bores 584 and securedin tapped holes 591, secure stator 570 to rear endplate 518. Stator 570is thus positively located and aligned relative to shaft 502.

Rotors 530 and 532 are mounted on shaft 502 for rotation with the shaft.Stators 568; and 570 are closely received within rotors 530 and 532,separated from rotors 530 and 532 by a small air gap AG. (see, e.g.,FIG. 1F) Front endplate 516, bearing sleeve 186, front bearing 122, rearbearing 130, rear endplate 518, outer casing 520 and tie rods 524cooperate as a support assembly to maintain alignment of shaft 502,rotors 530 and 532, and stators 568 and 570. Shaft 502 is maintained bybearing sleeve 186, bearings 122 and 130, which are mounted on frontendplate 516 and rear endplate 518, respectively, and rotatably maintainand align shaft 502 concentric and perpendicular with the endplates.Rotors 530 and 532 are mounted for rotation on shaft 502, positivelypositioned by cooperation with tapered shaft portions 504 and 506. Frontendplate 516 mounts and locates stator 568 so that it is disposed withinrotor 530 properly aligned with shaft 502 and rotor 530. Rear endplate518 mounts and locates stator 570 so that it is disposed within rotor532 properly aligned with shaft 502 and rotor 532. Outer casing 520 hasend faces perpendicular to its axis (is preferably cylindrical) and isdisposed between front endplate 516 and rear endplate 518. Tie rods 524;compress endplates 516 and 518 against outer casing 520, keeping thecomponents squared and in alignment.

Referring again to FIG. 5F, a cooling airflow is directed over statorwindings 572 of stator 568 (preferably through loosely wrapped rear-sideand front-side end turns 523 and 525 respectively) and over statorwindings 574 of stator 570 (preferably through loosely wrapped rear-sideand front-side end turns 527 and 529 respectively) by employing acooling system comprising air intake vents 522, inter-rotor spatial gap531, rotor air passages 560 and 558, stator central apertures 580 and582 rear endplate 518 air passageways 533 bounded by adjacent rear endplate crossarms 517, outer portion 515, and hub 509 and front end plate516 air passages 535 bounded by adjacent rear end plate crossarms 501,outer portion 598, and hub 592 and fans 537 and 539. Air enteringinter-rotor spatial gap 531 between rotors 530 and 532 through airintake vents 522 of outer case 520 splits with half the airflow enteringrotor air passages 560 and the other half entering rotor air passages558. Air flow leaving rotor air passage 560 is directed over front-sideend turns 529 of stator winding 574. After leaving front end turns 529,airflow enters stator 570 central aperture 582 with cooperation of rotordeflector 590 and is then directed over loosely wrapped rear end turns527 of stator windings 574 by virtue of suitable relative disposition orcontouring, or, as in the embodiment of FIG. 5D, cooperation with a reardeflector 535. Air flow then enters passageways 533 bounded by adjacentrear end plate crossarms 517, outer portion 515, and hub 509 in rear endplate 518 and is driven by fan 539 which is mounted to shaft 502 by nut589. Airflow leaving rotor air passage 558 is directed over rear-sideend turns 523 of stator winding 572. After leaving rear end turns 523,airflow enters stator 568 central aperture 580 with cooperation ofdeflector 541 and is then directed over loosely wrapped front end turns525 of stator windings 574 by virtue of suitable relative disposition orcontouring, or, as in the embodiment of FIG. 5D, cooperation with afront deflector 587. Airflow then enters passageways 535 bounded byadjacent front end plate outer portion 598, crossarms 501, and hub 592in front end plate 516 and is driven by fan 537. In the preferredembodiment, centrifugal fan 537 is mounted for rotation with shaft 502between pulley 136 and front end plate 516 and centrifugal fan 539 ismounted for rotation with shaft 502 between nut 589 and rear end plate518 The cross sections, contours (turns and edges) and relativedispositions of the various air passageways are preferably chosen tominimize decreases in air velocity, and maximize airflow over end turns523 and 525 of stator 568 and end turns 527 and 529 of stator 570.

More specifically, cooling air, generally indicated by arrows 541 isintroduced into alternator 500 through air intake vents 522 and entersinter-rotor spatial gap 531. Airflow 543 splits into four distinctairflow paths, 545, 547, 549 and 551. Airflow 545 enters rotorpassageway 558 and impinges on stator end turns 523. After leaving endturns 523 airflow 545 is re-directed by rotor air deflector 541 andenters aperture 576 of stator 568. Airflow 545 is then re-directed overend turns 525 by use of front endplate air deflector 587 then leavesstator 500 through air passages 535 driven by fan 537. Airflow 547 movesbetween rotor casing 538 and outer case 520 thereby cooling magnets 542that are attached to rotor casing 538. Airflow 547 then impinges on endturns 525 after which it enters air passageway 535 leaving alternator500 driven by fan 537. Airflow 549 enters rotor passageway 560 andimpinges on stator end turns 529. After leaving end turns 529, airflow549 is re-directed by rotor air deflector 590 and enters aperture 582 ofstator 570. Airflow 549 is then re-directed over end turns 527 by use ofrear endplate air deflector 535 then leaves stator 500 through airpassages 533 driven by fan 539. Airflow 551 moves between rotor casing540 and outer case 520 thereby cooling magnets 544 that are attached torotor casing 540. Airflow 551 then impinges on end turns 527 after whichit enters air passageway 533 leaving alternator 500 driven by fan 539.Airflows 545 and 547 cool front components, specifically end turns 523and 525 as well as magnets 542 and airflows 549 and 551 cool rearcomponents, specifically end turns 529 and 527 as well as magnets 544.

Although effective in cooling components of alternator 500, air intakes522 may not always be possible for all applications, in which case, anair flow path similar to that of alternator 300 must be utilized.

Referring now to FIG. 5G, Alternator 555 suitably includes a shaft 557including two tapered projecting portions, 559 and 561 and two threadedportions 561 and 593; two jam nuts 512 and 514; front end plate 516; afront bearing 122; bearing sleeve 186; rear endplate 518, rear shaftretaining rings 128; a rear bearing 130; twin rotors 526 and 528;stators 568 and 570; an outer case 573 and respective tie rods 595. Twinrotors 530 and 532, as best seen in FIG. 5G, both preferably comprise anendcap 534 and 536, a cylindrical casing 538 and 540 respectfully and apredetermined number (e.g. 8 pairs) of alternatively poled permanentmagnets 542 disposed in the interior side wall of casing 538 and apredetermined number (e.g. 8 pairs) of alternatively poled permanentmagnets 544 disposed in the interior side wall of casing 540.

Rotors 530 and 532 are suitably substantially open, including peripheralportions 546 and 548 respectfully, and respective cross-arms 550 and 552and a central rotor hubs 554 and 556 respectfully to provide forconnection to shaft 502. Respective air passageways 558 are providedthrough endcap 534, bounded by peripheral portion 546, adjacent crossarms 550, and central hub 554. Respective air passageways 560 areprovided through endcap 536, bounded by peripheral portion 548, adjacentcross arms 552, and central hub 556. Central rotor hubs 554 and 556include through-bores 562 and 564 respectively having a predeterminedtaper (e.g. 1 in. per foot) corresponding to that of shaft portion 559and 561. In assembly, shaft 502 is journaled through both bores 562 and564, such that shaft tapered portions 559 and 561 are received in bores562 and 564 just forward of threaded shaft portions 561 and 563.Threaded shaft portions 561 and 563 cooperate with jam nuts 514 and 516to positively locate rotors 530 and 532 on shaft 502. As was previouslydescribed, the thickness of crossarms 550 and 552 are suitably chosen tobe as thin as possible (to minimize weight and material cost) whilestill capable of withstanding expected loads. Rotors 530 and 532 aremounted in close proximity axially on shaft 557 such that when rotor 530is seated on tapered portion 559 and rotor 532 is seated on taperedportion 561 a small gap 565 remains after assembly. This assures therotors will have proper clearance to fully seat when torque is appliedto bolts 512 and 514 respectively. Rotor air passages 558 and 560 arealigned during assembly to create an uninterrupted cooling fluidpassageway.

Stators 568 and 570 suitably comprise cores 583 and 585 and conductivewindings 572 and 574 respectively. Stators 568 and 570 cores suitablycomprises laminated stack of thin sheets of soft magnetic material, e.g.non-oriented, low loss (lead free) steel, that are cut or punched to thedesired shape, aligned and joined (e.g. welded or epoxied together in aprecision jig to maintain the separate laminations in alignment).Stators 568 and 570 cores are generally cylindrical, with an axiallycrenellated outer peripheral surface, i.e., includes a predeterminednumber of teeth 158 and slots 160. Both stator 568 and 570 arepreferably substantially open, with stator 568 having a central aperture576 and suitably includes crossarms 575, radial locating feature 577 andaxial through-bores 578 to facilitate mounting to front endplate 516using mounting bolts 580 and stator 570 having a central aperture 582and suitably includes crossarms 575, radial locating feature 581 andaxial through-bores 584 to facilitate mounting to rear endplate 518using mounting bolts 586.

Windings 572 and 574, formed of a suitably insulated electricalconductor, preferably varnished copper motor wire, are provided on cores583 and 585 of stator 568 and 570 respectively, wound through respectiveslots 160, outwardly along the side face of cores around a predeterminednumber of teeth 158, then back through another slot.

In assembly, stator 568 is disposed coaxially with rotor 530 and isclosely received within interior cavity of rotor 530. As will beexplained, front endplate 516 mounts and locates front stator 568 sothat it is properly aligned within internal chambers of rotor 530 andstator 570 is disposed coaxially with rotor 532 and is closely receivedwithin interior cavity of rotor 532. As will be explained, rear endplate518 mounts and locates rear stator 570 so that it is properly alignedwithin internal chambers of rotor 532. The peripheral surface of stators568 and 570 are separated from the interior surface of magnets 542 and544 respectively by a small predetermined air gap AG (see, e.g., FIG.1F):

Front endplate 516 suitably includes a stepped central hub 592 having aforward reduced diameter portion 594 and central aperture 596 therethrough, and a generally cylindrical outer peripheral portion 598,preferably having the same outer profile as rear endplate 518, connectedto hub 592 by respective crossarms 501. Respective counter bored holes503 are provided cylindrical outer peripheral portion 598. Apredetermined number of tapped holes 553 (e.g. 4) corresponding tostator crossarm bores 578 are provided in the stepped surface of hub592. Reduced diameter portion 594 is substantially equal to (butslightly less than) the diameter of the concentric radial locatingfeatures 577 on crossarms 575 of stator 568, so that front endplateportion 594 may be closely received within the concentric radiallocating features 577 on crossarms 575 of stator 568. Front bearingsleeve 186 is closely received within counter bore 505 of front endplatehub 592 and thus centers bearing 122 and shaft 502. Stator 568 ismounted on hub 592, with reduced diameter hub portion 594 receivedwithin the concentric radial locating features 577 on crossarms 575 ofstator 568 and the stator front sidewall against the hub step.Respective bolts 580 journaled through bores 578 and secured in tappedholes 553, secure stator 568 to front endplate 516. Stator 516 is thuspositively located and aligned relative to shaft 502.

Rear endplate 518 carries and locates rear bearing 130, mounts andlocates stator 570. Rear endplate 518 suitably includes a steppedcentral hub 509 having a forward reduced diameter portion 511 andcentral aperture 513 there through, and a generally cylindrical outerperipheral portion 515, preferably having the same outer profile asfront endplate 516, connected to hub 509 by respective crossarms 517.Respective tapped holes 519 are provided cylindrical outer peripheralportion 515, at the same radial distance from center and angulardispositions as counter bored holes 503 in front endplate 516. Apredetermined number of tapped holes 591 (e.g. 4) corresponding tostator crossarm bores 584 are provided in the stepped surface of hub509. The outer diameter of reduced diameter portion 511 is substantiallyequal to (but slightly less than) the diameter of the concentric radiallocating features 581 on crossarms 579, so that rear endplate portion511 may be closely received within the concentric radial locatingfeatures 581 on crossarms 579 of stator 570. Rear bearing 130 is closelyreceived within aperture 513 of rear endplate hub 509 and thus centersshaft 502. Stator 570 is mounted on hub 509, with reduced diameter hubportion 511 received within the concentric radial locating features 581on crossarms 579 of stator 570 and the stator rear sidewall against thehub step. Respective bolts 586 journaled through bores 584 and securedin tapped holes 519, secure stator 570 to rear endplate 518. Stator 570is thus positively located and aligned relative to shaft 502.

Rotors 530 and 532 are mounted on shaft 502 for rotation with the shaft.Stators 568; and 570 are closely received within rotors 530 and 532,separated from rotors 530 and 532 by a small air gap AG. (see, e.g.,FIG. 1F) Front endplate 516, bearing sleeve 186, front bearing 122, rearbearing 130, rear endplate 518, outer casing 520 and tie rods 524cooperate as a support assembly to maintain alignment of shaft 502,rotors 530 and 532, and stators 568 and 570. Shaft 502 is maintained bybearing sleeve 186, bearings 122 and 130, which are mounted on frontendplate 516 and rear endplate 518, respectively, and rotatably maintainand align shaft 502 concentric and perpendicular with the endplates.Rotors 530 and 532 are mounted for rotation on shaft 502, positivelypositioned by cooperation with tapered shaft portions 557 and 559. Frontendplate 516 mounts and locates stator 568 so that it is disposed withinrotor 530 properly aligned with shaft 502 and rotor 530. Rear endplate518 mounts and locates stator 570 so that it is disposed within rotor532 properly aligned with shaft 502 and rotor 532. Outer casing 520 hasend faces perpendicular to its axis (is preferably cylindrical) and isdisposed between front endplate 516 and rear endplate 518. Tie rods 597;compress endplates 516 and 518 against outer casing 573, keeping thecomponents squared and in alignment.

Referring again to FIG. 5G, a cooling airflow is directed over statorwindings 574 of stator 570 (preferably through loosely wrapped rear-sideand front-side end turns 527 and 529 respectively) by employing acooling system comprising air passageways 533 in rear end plate 518,stator 570 central aperture 582, rotor air passages 558 and 560, stator568 central aperture 576 and front end plate air passages 535. Airentering rear end plate air passage way 533 is directed to impinge onrear-side end turns 527 of windings 518, Air exiting stator centralaperture 582 is directed to impinge on windings 574 (front-side endturns 529), by virtue of suitable relative disposition or contouring,or, as in the embodiment of FIG. 5G, cooperation with rotor deflector590. Air exiting rotor air passages 558 and 560 is directed to impingeon windings 572 of stator 568 (preferably through loosely wrappedrear-side and front-side end turns 523 and 525 respectively). Afterpassing over rear-side end turns 523 is then directed to stator 568central aperture 576 by use of rotor deflector 541 then over front-sideend turns 525 then through front endplate 516 air passageway 535. Anasynchronous forced air supply, e.g., electric fan as outline byLafontaine et al., may be mounted on the back of rear end plate 518 toenhance air flow. In the preferred embodiment, centrifugal fan 138 ismounted for rotation with shaft 557 between pulley 136 and front endplate 516. The cross sections, contours (turns and edges) and relativedispositions of the various air passageways are preferably chosen tominimize decreases in air velocity, and maximize airflow over end turns527, 529 of stator 570 and end turns 523, 525 of stator 570.

More specifically, cooling air, generally indicated by arrows 567 isintroduced into alternator 555 through rear end plate air passageways533. Airflow 567 impinges upon rear end turn 527. Airflow 567 thensplits into respective streams 571 and 569. After exiting the end turns527, air stream 571 flows through stator 570 central aperture 582,impinges upon rotor deflector 590, is directed through the front-sideloosely wrapped end turns 529, rotor passageways 558 and 560, then withcooperation of rotor deflector 541, impinges on end turns 523 of stator568 is directed into stator 568 central aperture 576 then partialimpinges on end turns 525 and then exits alternator 555 through airpassageways 535 in front end plate 516. Air stream 569, after exitingrear-side end turns 527, flows between the outside of rotor casings 538and 540 and the inside of outer case 573 then impinges on front side endturns 525 of stator 568 then exits alternator 555 through airpassageways 535 in front end plate 516. Air stream 569 provides coolingof magnets 544, 542 and end turns 574, 525. Air stream 571 providescooling for end turns 527, 529, 523 and 525.

The effects of magnetic fringing are well known and can be utilized toincrease power of a permanent magnet machine. In conventional permanentmagnet machines the length of magnets are generally equal to the statorlength. If given the opportunity to extend the length of the magnetbeyond both stator faces, the magnetic fringing fields created wouldextend beyond the stator and intercept the winding end turns which alsoextend beyond the stator. Therefore, in an embodiment, permanent magnetshave predetermined lengths that exceeds predetermined stator facelengths, and in an embodiment with a plurality of stators, thepredetermined length of multiple pluralities of magnets may exceed facelengths of respective stator face lengths. The result is an overallincrease in flux interacting with the windings that in turn producesmore power for a given length of stator.

Referring now to FIGS. 6A and 6B, Alternator 600, which is very similarto alternator 100 in all regards except that of rotor 602, conforms toSAE proposed pad mount standard version 2-3, and in accordance withvarious aspects of the present invention comprises: a shaft 110,preferably including a tapered projecting portion 112 and a threadedportion 114 (best seen in FIG. 1E); a stator 118; a front endplate 120;a front bearing 122; a jam nut 124; a rear endplate 126; a rear shaftretaining rings 128; a rear bearing 130; an outer casing 132 andrespective tie rods (not shown). Rotor 602 is mounted on shaft 110 forrotation with the shaft 110. Stator 118 is closely received within rotor602, separated from rotor 602 by a small air gap AG (see, e.g., FIG.1F). Front endplate 120, bearing sleeve 186, front bearing 122, rearbearing 130, rear endplate 126, outer casing 132 and tie rods (notshown) cooperate as a support assembly to maintain alignment of shaft110, rotor 602, and stator 118. Shaft 110 is maintained by bearings 122and 130, which are mounted on front endplate 120 and rear endplate 126,respectively, and rotatably maintain and align shaft 110 concentric andperpendicular with the endplates. Rotor 602 is mounted for rotation onshaft 110, positively positioned by cooperation with tapered shaftportion 112. Rear endplate 126 mounts and locates stator 118 so that itis disposed within rotor 116 properly aligned with shaft 110 and rotor602. Outer casing 132 has end faces perpendicular to its axis (ispreferably cylindrical) and is disposed between front endplate 120 andrear endplate 126. Tie rods (not shown); compress endplates 120 and 126against outer casing 132, keeping the components squared and inalignment.

As best seen in FIG. 6B, rotor 602 preferably comprises an endcap 604, acylindrical casing 606 and a predetermined number (e.g. 8 pairs) ofalternatively poled permanent magnets 608 disposed in the interior wallof casing 606.

Magnets 608 extend past stator face 610 and 612 of stator 118. Ideallythe extension past the stator face 604 and 606 should be of equal lengthon both sides and in the range of 3/16 to 5/16 of an inch. Increasesbeyond that are of little benefit magnetically and only add to theoverall cost of an alternator. Since rare earth magnets are one of themost expensive components of a permanent magnet alternator, it isbeneficial to only use the minimum amount of magnet material needed toproduce the desired output.

As described by Lafontaine et al., cogging can present undesirableeffects during operation of a permanent magnet machine. When consideringdual rotor alternators the effects of cogging are greatly magnified dueto the increased overall length of stator, rotor and magnets. Skewingthe laminations eliminates the majority of these effects. Due to thenature of rare earth magnets i.e. the magnets must be kept below acertain temperature (curie temperature) to prevent permanentdemagnetization, it would be beneficial to develop a method that bothallows the skewed stator to be mounted to the rear endplate whileminimizing the impact to cooling fluids.

Referring now to FIGS. 7A-7F, stator 700 is suitably comprised of alaminated stack of thin sheets of soft magnetic material, e.g.non-oriented, low loss (lead free) steel, with a core 702 and conductivewindings (not shown). Stator 700 is preferably substantially open with acentral aperture 704 defined by the cylindrical interior surface 706 ofcore 704 with suitable crossarms 708 and radial locating features 710including cylindrical through bores 718 to fasten stator 700 to endplate720. The lamination sheets are generally cylindrical, with an axiallycrenellated outer peripheral surface, i.e., including a predeterminednumber of teeth 714 and slots 716 that are cut or punched to the desiredshape, aligned and joined (e.g., welded or epoxied together in aprecision jig to maintain the separate laminations in predeterminedalignment).

As best seen in FIG. 7B, the use of cylindrical through bores 718 formounting a skewed stator is ineffective since the overall axialcross-sectional area of the through bore is reduced due to theprogressive skewing of adjacent sheets. This progressive reduction incross-sectional area makes it impossible for mounting bolts 722 to bejournaled through bores 718 to endplate 720 and still maintainperpendicularity due to the interference at point 724. The use of aclamping ring as described by Lafontaine et al. to hold stator 700 isalso less than optimal in that it reduces the effective diameter of thecentral aperture of stator central aperture 706 to cooling fluids. Asbest seen in FIG. 7C, clamp ring 732 is used to hold down stator 700with cooperation of bolts 722. The result is reduced diameter portion734 of clamp 732.

To overcome the progressive reduction in cross-sectional area ofcylindrical through bores in a skewed stator and maximize air flow,crossarms 710 should suitably include radially slotted holes 726 tofacilitate mounting core 700 to endplate 720. Optimally, as described byLafontaine et al., the total angular skew from stator face 728 to statorface 730 is the angle created between adjacent teeth of a statorlamination (See FIG. 7A). Therefore to calculate angular skew, .dividethe total number of stator teeth by 360°. In the case of a 48 toothstator, it is 360/48 or 7.50° of skew. To assure adequate clearance forbolts 722 in through bores 732, the arc circumscribing radial slot 726must be equal to or slightly greater that the angle created by thedesired skew (7.50° in a 48 tooth stator) to assure proper clearance(see FIGS. 7E and 7F). As best seen in FIG. 7G, the radially slottedthrough-bores 732 allow mounting bolts 722 to thread into holes 738 andremain perpendicular to endplate 720 mounting surface 734. It would bebeneficial to include washer 736 to distribute the clamping forcesapplied to stator 700 since radial slots eliminates some of the clampingsurface that would otherwise be available in a cylindrical through bore.This method of mounting stator 700 allows for the greatest possiblecross-sectional area of cooling fluid to pass through the centralaperture of stator 700.

As described above, skewing the stator laminations one full tootheliminates cogging. A stator that has been skewed to that degree willexperience a loss in flux density due to the interaction of both magnetsand skewed coils as the rotor rotates. A unique opportunity to reducecogging without adversely affecting flux density can be attained in adual rotor configuration.

Referring now to FIGS. 8A and 8B, rotor 800 comprises a cylindricalrotor case 802; central support plate 804 and magnets 806 and 808.Magnets 806 are evenly disposed radially within cylindrical rotor case802. Magnets 808 are also evenly disposed radially within cylindricalrotor case 802. The axial edge of magnets 808 is positioned within rotorcase 802 such that witness line 810 created by the edge of magnet 808bisects the central axis of magnet 806.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. All changes which come within the meaning and rangeof equivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. A power conversion apparatus comprising: a shaft,a first stator, a second stator, a first rotor and a diametricallyopposed second rotor, the shaft, stators, and rotor casings beingcoaxially disposed with the rotor casings mounted on the shaft, thefirst and second stators including at least one winding; the first rotorincluding a first plurality of permanent magnets disposed proximate tothe first stator, separated from the first stator by a predetermined gapdistance, such that relative motion of the first stator and first rotorcauses magnetic flux from the magnets to magnetically interact with thefirst stator winding; the second rotor including a second plurality ofpermanent magnets disposed proximate to the second stator, separatedfrom the second stator by a predetermined gap distance, such thatrelative motion of the second rotor and second stator causes magneticflux from the magnets to magnetically interact with the second statorwinding, wherein the respective permanent first and second plurality ofmagnets have a predetermined length beyond a predetermined first andsecond stators individual face lengths; wherein the apparatus furthercomprises four lugs that couple the apparatus to a surface; wherein thedisposition of at least one of a first stator slot and a second statorslot and respective permanent magnets is skewed by a predeterminedamount relative to the axis of the first and second stator; and whereinthe first rotor and stator pairing and second rotor and stator pairingcomprise independent output voltages.
 2. The apparatus of claim 1wherein the independent output voltages comprise a direct current and analternating current.
 3. The apparatus of claim 2 wherein the first rotorand first stator pairing and second rotor and second stator pairings areconfigured to provide an output voltage range optimized for 12 VDC and asecond independent voltage range optimized for 110 VAC.
 4. The apparatusof claim 1 wherein the shaft has a predetermined diameter and includesshaft tapered portions disposed between the ends of the shaft atpredetermined positions relative to the first and second stators, thediameter of the shaft tapered portions varying in accordance with apredetermined taper from a minimum diameter to a predetermined maximumdiameter greater than the shaft predetermined diameter; and the firstand second rotors include a hub and a central through-bore having thepredetermined taper corresponding to a taper of at least one shafttapered portion of the shaft, the diameter of the tapered through-borevarying in accordance with the predetermined taper from a minimumthrough-bore diameter greater than the shaft predetermined diameter to apredetermined maximum through-bore diameter; and the first and secondrotors hub are disposed with the shaft journaled and extending throughthe hub through-bore, with the shaft tapered portion received in thethrough-bore with interior surface of the through bore and exteriorsurface of the shaft tapered portion in mating contact, whereincooperation of the tapered first and second rotor bore is in surfacecontact with the shaft tapered portion positions the first and secondrotors both axially and radially with respect to the shaft and first andsecond stators, coupling the first and second rotors to the shaft forrotation therewith.
 5. The apparatus of claim 1 wherein the first andsecond rotors and shaft comprise an integral unit.
 6. The apparatus ofclaim 1 wherein the shaft is rotatably coupled to a first endplate. 7.The apparatus of claim 7 wherein the first and second rotors compriseendcaps coupling a cylindrical casing to the shaft; the casing andendcaps comprising an integral unit.